Merge pull request 'Implement relationships in the ECS' (#3) from feature/ecs-relations into main

Reviewed-on: #3

examples/testbed/src/free_fly_camera.rs

@@ -1,8 +1,5 @@
 use lyra_engine::{
-    game::Game,
-    input::{ActionHandler, CommonActionLabel},
-    math::{Quat, Vec3, EulerRot},
-    plugin::Plugin, ecs::{Component, query::{Res, View}}, DeltaTime, scene::CameraComponent,
+    ecs::{query::{Res, View}, Component}, game::Game, input::ActionHandler, math::{EulerRot, Quat, Vec3}, plugin::Plugin, scene::CameraComponent, DeltaTime
 };
 
 /* enum FreeFlyCameraActions {

examples/testbed/src/main.rs

@@ -1,6 +1,6 @@
 use std::ptr::NonNull;
 
-use lyra_engine::{math::{self, Vec3}, math::Transform, input::{KeyCode, ActionHandler, Action, ActionKind, LayoutId, ActionMapping, ActionSource, ActionMappingId, InputActionPlugin, MouseInput, MouseAxis, CommonActionLabel}, game::Game, render::{window::{CursorGrabMode, WindowOptions}, light::{PointLight, directional::DirectionalLight, SpotLight}}, change_tracker::Ct, ecs::{system::{Criteria, CriteriaSchedule, BatchedSystem, IntoSystem}, world::World, Component}, DeltaTime, scene::{ModelComponent, CameraComponent}, lua::{LuaScriptingPlugin, LuaScript}, Script, ScriptList};
+use lyra_engine::{math::{self, Vec3}, math::Transform, input::{KeyCode, ActionHandler, Action, ActionKind, LayoutId, ActionMapping, ActionSource, ActionMappingId, InputActionPlugin, MouseInput, MouseAxis, CommonActionLabel}, game::Game, render::{window::{CursorGrabMode, WindowOptions}, light::{PointLight, directional::DirectionalLight, SpotLight}}, change_tracker::Ct, ecs::{system::{Criteria, CriteriaSchedule, BatchedSystem, IntoSystem}, World, Component}, DeltaTime, scene::{ModelComponent, CameraComponent}, lua::{LuaScriptingPlugin, LuaScript}, Script, ScriptList};
 use lyra_engine::assets::{ResourceManager, Model};
 
 mod free_fly_camera;
@@ -88,6 +88,7 @@ async fn main() {
         //let cube_model = resman.request::<Model>("assets/cube-texture-bin.glb").unwrap();
         let cube_model = resman.request::<Model>("assets/texture-sep/texture-sep.gltf").unwrap();
         let crate_model = resman.request::<Model>("assets/crate/crate.gltf").unwrap();
+        //let sponza_model = resman.request::<Model>("assets/sponza/Sponza.gltf").unwrap();
         drop(resman);
 
         /* world.spawn((
@@ -95,6 +96,11 @@ async fn main() {
             Transform::from_xyz(0.0, -5.0, -10.0),
         )); */
 
+        /* world.spawn((
+            ModelComponent(sponza_model),
+            Transform::from_xyz(0.0, 0.0, 0.0),
+        )); */
+
         {
             let cube_tran = Transform::from_xyz(-3.5, 0.0, -8.0);
             //cube_tran.rotate_y(math::Angle::Degrees(180.0));

lyra-ecs/src/archetype.rs

@@ -1,4 +1,4 @@
-use std::{ptr::{NonNull, self}, alloc::{self, Layout, alloc, dealloc}, mem, collections::HashMap, cell::{RefCell, Ref, RefMut, BorrowError, BorrowMutError}, ops::{DerefMut, Deref}};
+use std::{ptr::{NonNull, self}, alloc::{self, Layout, alloc, dealloc}, mem, collections::HashMap, cell::{RefCell, Ref, RefMut, BorrowError, BorrowMutError}, ops::DerefMut};
 
 use crate::{world::ArchetypeEntityId, bundle::Bundle, component_info::ComponentInfo, DynTypeId, Tick, Entity};
 
@@ -18,9 +18,8 @@ impl Drop for ComponentColumn {
         let data = data.as_ptr();
 
         unsafe {
-            // layout of current alloc
-            let layout = Layout::from_size_align_unchecked(self.info.layout.size * self.capacity,
-                self.info.layout.alignment);
+            // TODO: trigger drop on the components
+            let layout = self.info.layout();
             dealloc(data, layout);
         }
     }
@@ -42,7 +41,7 @@ impl ComponentColumn {
     }
 
     pub unsafe fn new(info: ComponentInfo, capacity: usize) -> Self {
-        let data = ComponentColumn::alloc(info.layout.into_layout().unwrap(), capacity);
+        let data = ComponentColumn::alloc(info.layout(), capacity);
         
         Self {
             data: RefCell::new(data),
@@ -64,8 +63,9 @@ impl ComponentColumn {
         let mut data = self.data.borrow_mut();
         let data = data.deref_mut();
         
-        let dest = NonNull::new_unchecked(data.as_ptr().add(entity_index * self.info.layout.size));
-        ptr::copy_nonoverlapping(comp_src.as_ptr(), dest.as_ptr(), self.info.layout.size);
+        let size = self.info.layout().size();
+        let dest = NonNull::new_unchecked(data.as_ptr().add(entity_index * size));
+        ptr::copy_nonoverlapping(comp_src.as_ptr(), dest.as_ptr(), size);
 
         // check if a component spot is being set twice and that the entity's tick is
         // already stored
@@ -81,31 +81,33 @@ impl ComponentColumn {
     /// # Safety
     /// 
     /// This column MUST have the entity. If it does not, it WILL NOT panic and will cause UB.
-    pub unsafe fn get<T>(&self, entity_index: usize) -> &T {
+    pub unsafe fn get<T>(&self, entity_index: usize) -> Ref<T> {
         let data = self.data.borrow();
-        let data = data.deref();
 
+        Ref::map(data, |data| {
             let ptr = NonNull::new_unchecked(data.as_ptr()
-            .add(entity_index * self.info.layout.size))
+                .add(entity_index * self.info.layout().size()))
                 .cast();
             &*ptr.as_ptr()
+        })
     }
 
-    /// Get a component at an entities index.
+    /// Get a mutable borrow to the component at an entities index, ticking the entity.
     /// 
     /// # Safety
     /// 
     /// This column must have the entity.
-    pub unsafe fn get_mut<T>(&mut self, entity_index: usize, tick: &Tick) -> &mut T {
+    pub unsafe fn get_mut<T>(&mut self, entity_index: usize, tick: &Tick) -> RefMut<T> {
         self.entity_ticks[entity_index].tick_to(tick);
 
-        let mut data = self.data.borrow_mut();
-        let data = data.deref_mut();
+        let data = self.data.borrow_mut();
 
-        let p = data.as_ptr()
-            .cast::<T>()
-            .add(entity_index * self.info.layout.size);
-        &mut *p
+        RefMut::map(data, |data| {
+            let ptr = NonNull::new_unchecked(data.as_ptr()
+                .add(entity_index * self.info.layout().size()))
+                .cast();
+            &mut *ptr.as_ptr()
+        })
     }
 
     /// Grow the column to fit `new_capacity` amount of components.
@@ -123,17 +125,19 @@ impl ComponentColumn {
 
         let mut data = self.data.borrow_mut();
 
-        let mut new_ptr = Self::alloc(self.info.layout.into_layout().unwrap(), new_capacity);
+        let layout = self.info.layout();
+        let mut new_ptr = Self::alloc(layout, new_capacity);
 
         if self.len > 0 {
-            ptr::copy_nonoverlapping(data.as_ptr(), new_ptr.as_ptr(), self.len * self.info.layout.size);
+            ptr::copy_nonoverlapping(data.as_ptr(), new_ptr.as_ptr(), self.len * layout.size());
         }
 
         // dont attempt to free if we weren't able to store anything anyway
         if self.capacity != 0 {
+            // create a layout with the same alignment, but expand the size of the buffer.
             let old_layout = Layout::from_size_align_unchecked(
-                self.info.layout.size.checked_mul(self.capacity).unwrap(),
-                self.info.layout.alignment
+                layout.size().checked_mul(self.capacity).unwrap(),
+                layout.align()
             );
 
             mem::swap(data.deref_mut(), &mut new_ptr);
@@ -152,15 +156,16 @@ impl ComponentColumn {
         let mut data = self.data.borrow_mut();
         let data = data.deref_mut();
 
+        let size = self.info.layout().size();
         let mut old_comp_ptr = NonNull::new_unchecked(data.as_ptr()
-            .add(entity_index * self.info.layout.size));
+            .add(entity_index * size));
 
         let moved_index = if entity_index != self.len - 1 {
             let moved_index = self.len - 1;
             let mut new_comp_ptr = NonNull::new_unchecked(data.as_ptr()
-                .add(moved_index * self.info.layout.size));
+                .add(moved_index * size));
 
-            ptr::copy_nonoverlapping(new_comp_ptr.as_ptr(), old_comp_ptr.as_ptr(), self.info.layout.size);
+            ptr::copy_nonoverlapping(new_comp_ptr.as_ptr(), old_comp_ptr.as_ptr(), size);
 
             mem::swap(&mut old_comp_ptr, &mut new_comp_ptr); // new_comp_ptr is now the old ptr
 
@@ -193,6 +198,7 @@ impl ComponentColumn {
     }
 }
 
+/// An id of an Archetype
 #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, Default)]
 pub struct ArchetypeId(pub u64);
 
@@ -206,20 +212,41 @@ impl ArchetypeId {
     }
 }
 
+/// Stores a group of entities with matching components.
+/// 
+/// An Archetype can be thought of as a table, with entities as the rows and the entity's
+/// components as each column. This means you can have tightly packed components of entities and
+/// quickly iterate through entities with the same components.
 #[derive(Clone, Default)]
 pub struct Archetype {
-    pub id: ArchetypeId,
-    pub(crate) entities: HashMap<Entity, ArchetypeEntityId>,
+    id: ArchetypeId,
+    /// The indexes of the entities in the archetype.
+    pub(crate) entity_ids: HashMap<Entity, ArchetypeEntityId>,
     /// map an Archetype entity id to an entity
-    pub(crate) ids_to_entity: HashMap<ArchetypeEntityId, Entity>,
+    //pub(crate) ids_to_entity: HashMap<ArchetypeEntityId, Entity>,
+    /// The entities in the Archetype.
+    ///
+    /// Can be used to map `ArchetypeEntityId` to an Entity since `ArchetypeEntityId` has
+    /// the index that the entity is stored at.
+    pub(crate) entities: Vec<Entity>,
     pub(crate) columns: Vec<ComponentColumn>,
-    pub capacity: usize,
+    capacity: usize,
 }
 
 /// The default capacity of the columns
 const DEFAULT_CAPACITY: usize = 32;
 
 impl Archetype {
+    /// Returns the id of the Archetype
+    pub fn id(&self) -> ArchetypeId {
+        self.id
+    }
+
+    /// Returns the max amount of Entities that the Archetype can store without reallocating.
+    pub fn capacity(&self) -> usize {
+        self.capacity
+    }
+
     pub fn from_bundle_info(new_id: ArchetypeId, bundle_info: Vec<ComponentInfo>) -> Archetype {
         let columns = bundle_info.into_iter().map(|i| {
             unsafe { ComponentColumn::new(i, DEFAULT_CAPACITY) }
@@ -227,8 +254,8 @@ impl Archetype {
 
         Archetype {
             id: new_id,
-            entities: HashMap::new(),
-            ids_to_entity: HashMap::new(),
+            entity_ids: HashMap::new(),
+            entities: Vec::new(),
             columns,
             capacity: DEFAULT_CAPACITY,
         }
@@ -243,15 +270,16 @@ impl Archetype {
     where
         B: Bundle
     {
-        if self.capacity == self.entities.len() {
+        if self.capacity == self.entity_ids.len() {
             let new_cap = self.capacity * 2;
             self.grow_columns(new_cap);
             self.capacity = new_cap;
         }
 
-        let entity_index = ArchetypeEntityId(self.entities.len() as u64);
-        self.entities.insert(entity, entity_index);
-        self.ids_to_entity.insert(entity_index, entity);
+        debug_assert_eq!(self.entity_ids.len(), self.entities.len(), "Somehow the Archetype's entity storage got unsynced");
+        let entity_index = ArchetypeEntityId(self.entity_ids.len() as u64);
+        self.entity_ids.insert(entity, entity_index);
+        self.entities.push(entity);
 
         bundle.take(|data, type_id, _size| {
             let col = self.get_column_mut(type_id).unwrap();
@@ -262,61 +290,64 @@ impl Archetype {
         entity_index
     }
 
-    /// Removes an entity from the Archetype and frees its components. Returns the entity record that took its place in the component column.
+    /// Removes an entity from the Archetype and frees its components. Returns the entity record
+    /// that took its place in the component column.
     pub(crate) fn remove_entity(&mut self, entity: Entity, tick: &Tick) -> Option<(Entity, ArchetypeEntityId)> {
-        let entity_index = *self.entities.get(&entity)
+        let entity_index = *self.entity_ids.get(&entity)
             .expect("The entity is not in this Archetype!");
         let mut removed_entity: Option<(Entity, ArchetypeEntityId)> = None;
 
         for c in self.columns.iter_mut() {
             let moved_entity = unsafe { c.remove_component(entity_index.0 as usize, tick) };
 
-            // Make sure that the moved entity is the same as what was moved in other columns.
-            // If this is the first move, find the EntityId that points to the column index.
-            // If there wasn't a moved entity, make sure no other columns moved something.
             if let Some(res) = moved_entity {
-
                 if let Some((_, aid)) = removed_entity {
-                    assert!(res as u64 == aid.0); // make sure all columns removed the same entity
+                    // Make sure that the moved entity is the same as what was moved in other columns.
+                    assert!(res as u64 == aid.0);
                 } else {
-                    let replaced_entity = self.entities.iter().find(|(_, a)| a.0 == res as u64)
-                        .map(|(e, _a)| *e).expect("Failure to find entity for moved component!");
-                    removed_entity = Some((replaced_entity, ArchetypeEntityId(res as u64)));
+                    // This is the first move, so find the EntityId that points to the column index.
+                    let just_removed = self.entities[res];
+                    removed_entity = Some((just_removed, ArchetypeEntityId(res as u64)));
                 }
             } else {
+                // If there wasn't a moved entity, make sure no other columns moved something. 
                 assert!(removed_entity.is_none());
             }
         }
 
         // safe from the .expect at the start of this method.
-        self.entities.remove(&entity).unwrap();
-        self.ids_to_entity.remove(&entity_index).unwrap();
+        self.entity_ids.remove(&entity).unwrap();
+        if self.entities.len() > 1 {
+            let len = self.entities.len();
+            self.entities.swap(entity_index.0 as _,  len - 1);
+        }
+        self.entities.pop().unwrap();
         
         // now change the ArchetypeEntityId to be the index that the moved entity was moved into.
         removed_entity.map(|(e, _a)| (e, entity_index))
-
     }
 
     /// Returns a boolean indicating whether this archetype can store the TypeIds given
     pub fn is_archetype_for(&self, types: &Vec<DynTypeId>) -> bool {
         if types.len() == self.columns.len() {
-            self.columns.iter().all(|c| types.contains(&c.info.type_id))
+            self.columns.iter().all(|c| types.contains(&c.info.type_id()))
         } else { false }
     }
 
     /// Returns a boolean indicating whether this archetype has a column for `comp_type`
-    pub fn has_column(&self, comp_type: DynTypeId) -> bool {
-        self.columns.iter().any(|c| comp_type == c.info.type_id)
+    pub fn has_column<I: Into<DynTypeId>>(&self, comp_type: I) -> bool {
+        let comp_type = comp_type.into();
+        self.columns.iter().any(|c| comp_type == c.info.type_id())
     }
 
     /// Returns a boolean indicating whether this archetype is empty or not.
     pub fn is_empty(&self) -> bool {
-        self.entities.is_empty()
+        self.entity_ids.is_empty()
     }
 
     /// Returns the amount of entities that are stored in the archetype.
     pub fn len(&self) -> usize {
-        self.entities.len()
+        self.entity_ids.len()
     }
 
     /// Grows columns in the archetype
@@ -337,28 +368,32 @@ impl Archetype {
         self.capacity = new_capacity;
     }
 
-    pub fn get_column(&self, type_id: DynTypeId) -> Option<&ComponentColumn> {
-        self.columns.iter().find(|c| c.info.type_id == type_id)
+    /// Attempts to find the column storing components of `type_id`
+    pub fn get_column<I: Into<DynTypeId>>(&self, type_id: I) -> Option<&ComponentColumn> {
+        let type_id = type_id.into();
+        self.columns.iter().find(|c| c.info.type_id() == type_id)
     }
 
     /// Returns a mutable borrow to a component column for `type_id`.
     /// 
     /// Note: This does not modify the tick for the column!
-    pub fn get_column_mut(&mut self, type_id: DynTypeId) -> Option<&mut ComponentColumn> {
-        self.columns.iter_mut().find(|c| c.info.type_id == type_id)
+    pub fn get_column_mut<I: Into<DynTypeId>>(&mut self, type_id: I) -> Option<&mut ComponentColumn> {
+        let type_id = type_id.into();
+        self.columns.iter_mut().find(|c| c.info.type_id() == type_id)
     }
 
     /// Reserves a slot in the columns for an entity and returns the index of that reserved spot
     pub fn reserve_one(&mut self, entity: Entity) -> ArchetypeEntityId {
-        if self.capacity == self.entities.len() {
+        if self.capacity == self.entity_ids.len() {
             let new_cap = self.capacity * 2;
             self.grow_columns(new_cap);
             self.capacity = new_cap;
         }
 
-        let entity_index = ArchetypeEntityId(self.entities.len() as u64);
-        self.entities.insert(entity, entity_index);
-        self.ids_to_entity.insert(entity_index, entity);
+        debug_assert_eq!(self.entity_ids.len(), self.entities.len(), "Somehow the Archetype's entity storage got unsynced");
+        let entity_index = ArchetypeEntityId(self.entity_ids.len() as u64);
+        self.entity_ids.insert(entity, entity_index);
+        self.entities.push(entity);
 
         for col in self.columns.iter_mut() {
             col.len += 1;
@@ -370,8 +405,8 @@ impl Archetype {
     /// Moves the entity from this archetype into another one.
     /// 
     /// # Safety
-    /// The entity IS NOT removed from the old archetype. You must manually call [`Archetype::remove_entity`].
-    /// It was done this way because I had some borrow check issues when writing [`World::insert`]
+    /// The entity IS NOT removed from the old archetype. You must manually call [`Archetype::remove_entity`](crate::Archetype).
+    /// It was done this way because I had some borrow check issues when writing [`World::insert`](crate::World)
     /// related to borrowing mutably from self more than once.
     /* pub fn move_into<B>(&self, into_arch: &mut Archetype, entity: Entity, new_components: B)
     where
@@ -404,22 +439,29 @@ impl Archetype {
         //self.remove_entity(entity);
     } */
 
-    pub fn entities(&self) -> &HashMap<Entity, ArchetypeEntityId> {
-        &self.entities
+    /// Returns a borrow to the map used to find the column indices of the entity.
+    pub fn entity_indexes(&self) -> &HashMap<Entity, ArchetypeEntityId> {
+        &self.entity_ids
     }
 
-    pub fn entity_of_index(&self, id: ArchetypeEntityId) -> Option<Entity> {
-        self.ids_to_entity.get(&id).cloned()
+    /// Returns the Entity that is stored at the column matching `id`.
+    pub fn entity_at_index(&self, id: ArchetypeEntityId) -> Option<Entity> {
+        self.entities.get(id.0 as usize).cloned()
+    }
+
+    /// Returns a boolean indicating if the Archetype is storing the entity.
+    pub fn has_entity(&self, e: Entity) -> bool {
+        self.entity_ids.contains_key(&e)
     }
 }
 
 #[cfg(test)]
 mod tests {
-    use std::{alloc::Layout, ptr::NonNull};
+    use std::{alloc::Layout, cell::Ref, ptr::NonNull};
 
     use rand::Rng;
 
-    use crate::{bundle::Bundle, tests::{Vec2, Vec3}, ComponentInfo, DynTypeId, DynamicBundle, Entity, EntityId, MemoryLayout, Tick};
+    use crate::{bundle::Bundle, tests::{Vec2, Vec3}, ComponentInfo, DynTypeId, DynamicBundle, Entity, EntityId, Tick};
 
     use super::Archetype;
 
@@ -435,7 +477,7 @@ mod tests {
         let entity_arch_id = a.add_entity(entity, bundle, &Tick::default());
 
         let col = a.columns.get(0).unwrap();
-        let vec2: &Vec2 = unsafe { col.get(entity_arch_id.0 as usize) };
+        let vec2: Ref<Vec2> = unsafe { col.get(entity_arch_id.0 as usize) };
         assert_eq!(vec2.clone(), bundle.0);
     }
 
@@ -451,11 +493,11 @@ mod tests {
         let entity_arch_id = a.add_entity(entity, bundle, &Tick::default());
 
         let col = a.columns.get(0).unwrap();
-        let vec2: &Vec2 = unsafe { col.get(entity_arch_id.0 as usize) };
+        let vec2: Ref<Vec2> = unsafe { col.get(entity_arch_id.0 as usize) };
         assert_eq!(vec2.clone(), bundle.0);
 
         let col = a.columns.get(1).unwrap();
-        let vec3: &Vec3 = unsafe { col.get(entity_arch_id.0 as usize) };
+        let vec3: Ref<Vec3> = unsafe { col.get(entity_arch_id.0 as usize) };
         assert_eq!(vec3.clone(), bundle.1);
     }
 
@@ -477,9 +519,9 @@ mod tests {
         let earch2 = a.add_entity(e2, b2, &Tick::default());
 
         let col = a.columns.get(0).unwrap();
-        let vec2: &Vec2 = unsafe { col.get(earch1.0 as usize) };
+        let vec2: Ref<Vec2> = unsafe { col.get(earch1.0 as usize) };
         assert_eq!(vec2.clone(), b1.0);
-        let vec2: &Vec2 = unsafe { col.get(earch2.0 as usize) };
+        let vec2: Ref<Vec2> = unsafe { col.get(earch2.0 as usize) };
         assert_eq!(vec2.clone(), b2.0);
     }
 
@@ -501,15 +543,15 @@ mod tests {
         let earch2 = a.add_entity(e2, b2, &Tick::default());
 
         let col = a.columns.get(0).unwrap();
-        let vec2: &Vec2 = unsafe { col.get(earch1.0 as usize) };
+        let vec2: Ref<Vec2> = unsafe { col.get(earch1.0 as usize) };
         assert_eq!(vec2.clone(), b1.0);
-        let vec2: &Vec2 = unsafe { col.get(earch2.0 as usize) };
+        let vec2: Ref<Vec2> = unsafe { col.get(earch2.0 as usize) };
         assert_eq!(vec2.clone(), b2.0);
 
         let col = a.columns.get(1).unwrap();
-        let vec3: &Vec3 = unsafe { col.get(earch1.0 as usize) };
+        let vec3: Ref<Vec3> = unsafe { col.get(earch1.0 as usize) };
         assert_eq!(vec3.clone(), b1.1);
-        let vec3: &Vec3 = unsafe { col.get(earch2.0 as usize) };
+        let vec3: Ref<Vec3> = unsafe { col.get(earch2.0 as usize) };
         assert_eq!(vec3.clone(), b2.1);
     }
 
@@ -552,7 +594,7 @@ mod tests {
 
         let col = a.columns.get(0).unwrap();
         for i in 0..bundle_count {
-            let vec2: &Vec2 = unsafe { col.get(i) };
+            let vec2: Ref<Vec2> = unsafe { col.get(i) };
             assert_eq!(vec2.clone(), bundles[i].0);
         }
     }
@@ -599,7 +641,7 @@ mod tests {
     /// This test simulates an archetype that stores types that rust does not know about.
     #[test]
     fn dynamic_archetype() {
-        let layout = MemoryLayout::from(Layout::new::<u32>());
+        let layout = Layout::new::<u32>();
         let info = ComponentInfo::new_unknown(DynTypeId::Unknown(100), "u32", layout);
         let infos = vec![info.clone()];
 

lyra-ecs/src/bundle.rs

@@ -143,7 +143,7 @@ impl DynamicBundle {
 
 impl Bundle for DynamicBundle {
     fn type_ids(&self) -> Vec<DynTypeId> {
-        self.bundle.iter().map(|b| b.1.type_id).collect()
+        self.bundle.iter().map(|b| b.1.type_id()).collect()
     }
 
     fn info(&self) -> Vec<ComponentInfo> {
@@ -152,7 +152,7 @@ impl Bundle for DynamicBundle {
 
     fn take(self, mut f: impl FnMut(NonNull<u8>, DynTypeId, usize)) {
         for (data, info) in self.bundle.iter() {
-            f(*data, info.type_id, info.layout.size);
+            f(*data, info.type_id(), info.layout().size());
         }
     }
 

lyra-ecs/src/command.rs

@@ -2,30 +2,55 @@ use std::{any::Any, cell::RefMut, collections::VecDeque, ptr::{self, NonNull}};
 
 use crate::{system::FnArgFetcher, Access, Bundle, Entities, Entity, World};
 
+/// A Command be used to delay mutation of the world until after this system is ran.
 pub trait Command: Any {
     fn as_any_boxed(self: Box<Self>) -> Box<dyn Any>;
 
-    fn run(self, world: &mut World) -> anyhow::Result<()>;
+    /// Executes the command
+    fn run(self, world: &mut World);
 }
 
 impl<F> Command for F
 where
-    F: FnOnce(&mut World) -> anyhow::Result<()> + 'static
+    F: FnOnce(&mut World) + 'static
 {
     fn as_any_boxed(self: Box<Self>) -> Box<dyn Any> {
         self
     }
 
-    fn run(self, world: &mut World) -> anyhow::Result<()> {
+    fn run(self, world: &mut World) {
         self(world)
     }
 }
 
-type RunCommand = unsafe fn(cmd: Box<dyn Command>, world: &mut World) -> anyhow::Result<()>;
+type RunCommand = unsafe fn(cmd: Box<dyn Command>, world: &mut World);
 
+/// Stores a queue of commands that will get executed after the system is ran.
+/// 
+/// This struct can be inserted as a resource into the world, and the commands will be
+/// executed by the [`GraphExecutor`](crate::system::GraphExecutor) after the system is executed.
 #[derive(Default)]
 pub struct CommandQueue(VecDeque<(RunCommand, Box<dyn Command>)>);
 
+/// Used in a system to queue up commands that will run right after this system.
+/// 
+/// This can be used to delay the mutation of the world until after the system is ran. These
+/// must be used if you're mutating the world inside a [`ViewState`](crate::query::ViewState).
+/// 
+/// ```nobuild
+/// fn particle_spawner_system(
+///     commands: Commands,
+///     view: ViewState<(&Campfire, &Transform)>
+/// ) -> anyhow::Result<()> {
+///     for (campfire, pos) in view.iter() {
+///         // If you do not use commands to spawn this, the next iteration
+///         // of the view will cause a segfault.
+///         commands.spawn((pos, Particle::new(/* ... */)));
+///     }
+/// 
+///     Ok(())
+/// }
+/// ```
 pub struct Commands<'a, 'b> {
     queue: &'b mut CommandQueue,
     entities: &'a mut Entities,
@@ -48,20 +73,18 @@ impl<'a, 'b> Commands<'a, 'b> {
                 .downcast::<C>()
                 .unwrap();
             
-            cmd.run(world)?;
-
-            Ok(())
+            cmd.run(world);
         };
 
         self.queue.0.push_back((run_fn, cmd));
     }
 
+    /// Spawn an entity into the World. See [`World::spawn`]
     pub fn spawn<B: Bundle + 'static>(&mut self, bundle: B) -> Entity {
         let e = self.entities.reserve();
 
         self.add(move |world: &mut World| {
             world.spawn_into(e, bundle);
-            Ok(())
         });
 
         e
@@ -71,7 +94,7 @@ impl<'a, 'b> Commands<'a, 'b> {
     pub fn execute(&mut self, world: &mut World) -> anyhow::Result<()> {
         while let Some((cmd_fn, cmd_ptr)) = self.queue.0.pop_front() {
             unsafe {
-                cmd_fn(cmd_ptr, world)?;
+                cmd_fn(cmd_ptr, world);
             }
         }
 
@@ -114,7 +137,7 @@ pub fn execute_deferred_commands(world: &mut World, mut commands: RefMut<Command
 
 #[cfg(test)]
 mod tests {
-    use std::ptr::NonNull;
+    use std::{cell::Ref, ptr::NonNull};
 
     use crate::{system::{GraphExecutor, IntoSystem}, tests::Vec2, Commands, DynTypeId, World};
 
@@ -144,7 +167,7 @@ mod tests {
         // there's only one archetype
         let arch = world.archetypes.values().next().unwrap();
         let col = arch.get_column(DynTypeId::of::<Vec2>()).unwrap();
-        let vec2: &Vec2 = unsafe { col.get(3) };
+        let vec2: Ref<Vec2> = unsafe { col.get(3) };
         assert_eq!(vec2.clone(), spawned_vec);
     }
 }

lyra-ecs/src/component_info.rs

@@ -1,41 +1,4 @@
-use std::{any::TypeId, alloc::{Layout, LayoutError}};
-
-#[derive(Clone, Copy, Debug, PartialEq, Eq)]
-pub struct MemoryLayout {
-    pub size: usize,
-    pub alignment: usize
-}
-
-impl TryInto<Layout> for MemoryLayout {
-    type Error = LayoutError;
-
-    fn try_into(self) -> Result<Layout, Self::Error> {
-        Layout::from_size_align(self.size, self.alignment)
-    }
-}
-
-impl From<Layout> for MemoryLayout {
-    fn from(value: Layout) -> Self {
-        Self {
-            size: value.size(),
-            alignment: value.align(),
-        }
-    }
-}
-
-impl MemoryLayout {
-    pub fn new(size: usize, alignment: usize) -> Self {
-        MemoryLayout {
-            size,
-            alignment
-        }
-    }
-
-    /// Converts self into a Layout.
-    pub fn into_layout(self) -> Result<Layout, LayoutError> {
-        Layout::from_size_align(self.size, self.alignment)
-    }
-}
+use std::{any::TypeId, alloc::Layout};
 
 /// A dynamic type id. Supports types that are not known to Rust.
 #[derive(Clone, Copy, Hash, Debug, PartialEq, Eq)]
@@ -88,32 +51,38 @@ impl DynTypeId {
     }
 }
 
+/// Some information about a component.
 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
 pub struct ComponentInfo {
-    pub type_id: DynTypeId,
-    //pub name: String,
-    pub layout: MemoryLayout,
+    type_id: DynTypeId,
+    layout: Layout,
 }
 
 impl ComponentInfo {
     pub fn new<T: 'static>() -> Self {
         Self {
             type_id: TypeId::of::<T>().into(),
-            //name: type_name::<T>().to_string(),
-            layout: MemoryLayout::from(Layout::new::<T>()),
+            layout: Layout::new::<T>(),
         }
     }
 
     /// Create ComponentInfo from a type that is not known to rust
-    pub fn new_unknown<D>(type_id: D, name: &str, layout: MemoryLayout) -> Self
+    pub fn new_unknown<D>(type_id: D, name: &str, layout: Layout) -> Self
     where
         D: Into<DynTypeId>,
     {
         let _ = name; // would be used at some point
         Self {
             type_id: type_id.into(),
-            //name: name.to_string(),
             layout,
         }
     }
+    
+    pub fn type_id(&self) -> DynTypeId {
+        self.type_id
+    }
+
+    pub fn layout(&self) -> Layout {
+        self.layout
+    }
 }

lyra-ecs/src/lib.rs

@@ -7,39 +7,42 @@ pub(crate) mod lyra_engine {
     }
 }
 
-pub mod archetype;
 use std::ops::BitOr;
 
+mod archetype;
 pub use archetype::*;
 
-pub mod entity;
+mod entity;
 pub use entity::*;
 
-pub mod world;
+mod world;
 pub use world::*;
 
-pub mod command;
+mod command;
 pub use command::*;
 
-pub mod bundle;
+mod bundle;
 pub use bundle::*;
 
-pub mod component;
+mod component;
 pub use component::*;
 
 pub mod query;
 //pub use query::*;
 
-pub mod component_info;
+mod relation;
+pub use relation::Relation;
+
+mod component_info;
 pub use component_info::*;
 
-pub mod resource;
+mod resource;
 pub use resource::*;
 
 pub mod system;
 //pub use system::*;
 
-pub mod tick;
+mod tick;
 pub use tick::*;
 
 /// Implements Component for glam math types

lyra-ecs/src/query/borrow.rs

@@ -1,13 +1,12 @@
 use std::{marker::PhantomData, ptr::NonNull, cell::{Ref, RefMut}};
 
-use crate::{world::World, ComponentColumn, DynTypeId, Tick, Component};
+use crate::{World, ComponentColumn, DynTypeId, Tick, Component};
 
 use super::{Fetch, Query, AsQuery};
 
 /// Fetcher for borrowing components from archetypes.
 pub struct FetchBorrow<'a, T> {
     col: &'a ComponentColumn,
-    size: usize,
     _phantom: PhantomData<&'a T>
 }
 
@@ -22,13 +21,7 @@ where
     }
 
     unsafe fn get_item(&mut self, entity: crate::world::ArchetypeEntityId) -> Self::Item {
-        let ptr = self.col.borrow_ptr();
-        Ref::map(ptr, |ptr| {
-            let ptr = NonNull::new_unchecked(ptr.as_ptr()
-                .add(entity.0 as usize * self.size))
-                .cast();
-            &*ptr.as_ptr()
-        })
+        self.col.get(entity.0 as _)
     }
 }
 
@@ -81,17 +74,16 @@ where
     }
 
     fn can_visit_archetype(&self, archetype: &crate::archetype::Archetype) -> bool {
-        archetype.columns.iter().any(|c| c.info.type_id == self.type_id)
+        archetype.has_column(self.type_id)
     }
 
     unsafe fn fetch<'a>(&self, _world: &'a World, archetype: &'a crate::archetype::Archetype, tick: crate::Tick) -> Self::Fetch<'a> {
         let _ = tick;
-        let col = archetype.columns.iter().find(|c| c.info.type_id == self.type_id)
+        let col = archetype.get_column(self.type_id)
             .expect("You ignored 'can_visit_archetype'!");
 
         FetchBorrow {
             col,
-            size: col.info.layout.size,
             _phantom: PhantomData,
         }
     }
@@ -108,7 +100,6 @@ impl<T: Component> AsQuery for &T {
 /// A fetcher for mutably borrowing components from archetypes.
 pub struct FetchBorrowMut<'a, T> {
     col: NonNull<ComponentColumn>,
-    size: usize,
     tick: Tick,
     _phantom: PhantomData<&'a T>
 }
@@ -125,15 +116,7 @@ where
 
     unsafe fn get_item(&mut self, entity: crate::world::ArchetypeEntityId) -> Self::Item {
         let col = unsafe { self.col.as_mut() };
-        col.entity_ticks[entity.0 as usize] = self.tick;
-        let ptr = col.borrow_mut_ptr();
-
-        RefMut::map(ptr, |ptr| {
-            let ptr = NonNull::new_unchecked(ptr.as_ptr()
-                .add(entity.0 as usize * self.size))
-                .cast();
-            &mut *ptr.as_ptr()
-        })
+        col.get_mut(entity.0 as _, &self.tick)
     }
 }
 
@@ -188,13 +171,12 @@ where
     }
 
     fn can_visit_archetype(&self, archetype: &crate::archetype::Archetype) -> bool {
-        archetype.columns.iter().any(|c| c.info.type_id == self.type_id)
+        archetype.has_column(self.type_id)
     }
 
     unsafe fn fetch<'a>(&self, _world: &'a World, archetype: &'a crate::archetype::Archetype, tick: crate::Tick) -> Self::Fetch<'a> {
-        let col = archetype.columns.iter().find(|c| c.info.type_id == self.type_id)
+        let col = archetype.get_column(self.type_id)
             .expect("You ignored 'can_visit_archetype'!");
-        let layout_size = col.info.layout.size;
         let col = NonNull::from(col);
 
         // TODO: find a way to get the component column mutable with a borrowed archetype so its tick can be updated.
@@ -202,7 +184,6 @@ where
 
         FetchBorrowMut {
             col,
-            size: layout_size,
             tick,
             _phantom: PhantomData,
         }
@@ -219,9 +200,9 @@ impl<T: Component> AsQuery for &mut T {
 
 #[cfg(test)]
 mod tests {
-    use std::{mem::size_of, marker::PhantomData, ptr::NonNull};
+    use std::{marker::PhantomData, ptr::NonNull};
 
-    use crate::{archetype::{Archetype, ArchetypeId}, bundle::Bundle, query::{Fetch, View}, tests::Vec2, world::World, DynTypeId, Entity, EntityId, Tick};
+    use crate::{archetype::{Archetype, ArchetypeId}, bundle::Bundle, query::{Fetch, ViewState}, tests::Vec2, World, DynTypeId, Entity, EntityId, Tick};
 
     use super::{QueryBorrow, QueryBorrowMut, FetchBorrowMut};
 
@@ -244,7 +225,7 @@ mod tests {
             _phantom: std::marker::PhantomData,
         };
         let archetypes: Vec<&Archetype> = world.archetypes.values().collect();
-        let v = View::<QueryBorrow<Vec2>>::new(&world, borrow, archetypes);
+        let v = ViewState::<QueryBorrow<Vec2>, ()>::new(&world, borrow, (), archetypes);
 
         for e in v.into_iter() {
             println!("Found entity at {:?}", e);
@@ -260,7 +241,7 @@ mod tests {
             _phantom: std::marker::PhantomData,
         };
         let archetypes: Vec<&Archetype> = world.archetypes.values().collect();
-        let v = View::<QueryBorrowMut<Vec2>>::new(&world, borrow, archetypes);
+        let v = ViewState::<QueryBorrowMut<Vec2>, ()>::new(&world, borrow, (), archetypes);
 
         let mut orig = vec![];
 
@@ -277,7 +258,7 @@ mod tests {
             _phantom: std::marker::PhantomData,
         };
         let archetypes: Vec<&Archetype> = world.archetypes.values().collect();
-        let v = View::<QueryBorrow<Vec2>>::new(&world, borrow, archetypes);
+        let v = ViewState::<QueryBorrow<Vec2>, ()>::new(&world, borrow, (), archetypes);
 
         for (new, orig) in v.into_iter().zip(orig.iter()) {
             assert!(new.x - orig.x == 10.0);
@@ -298,12 +279,11 @@ mod tests {
             }, (Vec2::rand(),), &Tick::default());
         }
 
-        let col = a.columns.iter().find(|c| c.info.type_id == DynTypeId::of::<Vec2>()).unwrap();
+        let col = a.get_column(DynTypeId::of::<Vec2>()).unwrap();
 
         let mut bmut = FetchBorrowMut::<Vec2> {
             col: NonNull::from(col),
             tick: Tick::default(),
-            size: size_of::<Vec2>(),
             _phantom: PhantomData,
         };
         let item = unsafe { bmut.get_item(crate::ArchetypeEntityId(0)) };

lyra-ecs/src/query/dynamic/mod.rs

@@ -1,8 +1,8 @@
 use std::ptr::NonNull;
 
-use crate::{world::World, ComponentColumn, ComponentInfo};
+use crate::{World, ComponentColumn, ComponentInfo};
 
-pub mod view;
+mod view;
 pub use view::*;
 
 use super::Fetch;
@@ -15,7 +15,7 @@ pub struct DynamicType {
 
 impl DynamicType {
     pub fn is<T: 'static>(&self) -> bool {
-        self.info.type_id.is::<T>()
+        self.info.type_id().is::<T>()
     }
 }
 
@@ -38,7 +38,7 @@ impl<'a> Fetch<'a> for FetchDynamicType<'a> {
     unsafe fn get_item(&mut self, entity: crate::ArchetypeEntityId) -> Self::Item {
         let ptr = self.col.borrow_ptr();
         let ptr = NonNull::new_unchecked(ptr.as_ptr()
-            .add(entity.0 as usize * self.info.layout.size));
+            .add(entity.0 as usize * self.info.layout().size()));
 
         DynamicType {
             info: self.info,
@@ -63,11 +63,11 @@ impl QueryDynamicType {
     }
 
     pub fn can_visit_archetype(&self, archetype: &crate::archetype::Archetype) -> bool {
-        archetype.has_column(self.info.type_id)
+        archetype.has_column(self.info.type_id())
     }
 
     pub unsafe fn fetch<'a>(&self, _world: &'a World, _arch_id: crate::archetype::ArchetypeId, archetype: &'a crate::archetype::Archetype) -> FetchDynamicType<'a> {
-        let col = archetype.columns.iter().find(|c| c.info.type_id == self.info.type_id)
+        let col = archetype.get_column(self.info.type_id())
             .expect("You ignored 'can_visit_archetype'!");
 
         FetchDynamicType {

lyra-ecs/src/query/dynamic/view.rs

@@ -1,6 +1,6 @@
 use std::ops::Range;
 
-use crate::{world::World, Archetype, ArchetypeEntityId, ArchetypeId, query::Fetch};
+use crate::{World, Archetype, ArchetypeEntityId, ArchetypeId, query::Fetch};
 
 use super::{QueryDynamicType, FetchDynamicType, DynamicType};
 
@@ -83,7 +83,7 @@ impl<'a> Iterator for DynamicViewIter<'a> {
                 self.next_archetype += 1;
                 let arch = unsafe { self.archetypes.get_unchecked(arch_id) };
 
-                if arch.entities.is_empty() {
+                if arch.entity_ids.is_empty() {
                     continue;
                 }
 
@@ -94,7 +94,7 @@ impl<'a> Iterator for DynamicViewIter<'a> {
                 self.fetchers = self.queries.iter()
                     .map(|q| unsafe { q.fetch(self.world, ArchetypeId(arch_id as u64), arch) } )
                     .collect();
-                self.component_indices = 0..arch.entities.len() as u64;
+                self.component_indices = 0..arch.entity_ids.len() as u64;
             }
         }
     }
@@ -104,13 +104,13 @@ impl<'a> Iterator for DynamicViewIter<'a> {
 mod tests {
     use std::{alloc::Layout, ptr::NonNull};
 
-    use crate::{world::World, MemoryLayout, ComponentInfo, DynTypeId, DynamicBundle, query::dynamic::QueryDynamicType};
+    use crate::{World, ComponentInfo, DynTypeId, DynamicBundle, query::dynamic::QueryDynamicType};
 
     use super::DynamicView;
 
     #[test]
     fn single_dynamic_view() {
-        let comp_layout = MemoryLayout::from(Layout::new::<u32>());
+        let comp_layout = Layout::new::<u32>();
         let comp_info = ComponentInfo::new_unknown(DynTypeId::Unknown(100), "u32", comp_layout);
 
         let mut dynamic_bundle = DynamicBundle::default();

lyra-ecs/src/query/entities.rs

@@ -1,4 +1,4 @@
-use crate::{archetype::Archetype, world::World, Entity};
+use crate::{archetype::Archetype, World, Entity};
 
 use super::{Fetch, Query, AsQuery};
 
@@ -41,7 +41,7 @@ impl Query for Entities {
     unsafe fn fetch<'a>(&self, _world: &'a World, archetype: &'a Archetype, tick: crate::Tick) -> Self::Fetch<'a> {
         let _ = tick; // ignore unused warnings
         EntitiesFetch {
-            entities: archetype.entities.keys().cloned().collect::<Vec<Entity>>(),
+            entities: archetype.entity_ids.keys().cloned().collect::<Vec<Entity>>(),
         }
     }
 }

lyra-ecs/src/query/mod.rs

@@ -3,27 +3,27 @@ use crate::{archetype::Archetype, world::{ArchetypeEntityId, World}, Tick};
 pub mod view;
 pub use view::*;
 
-pub mod entities;
+mod entities;
 #[allow(unused_imports)]
 pub use entities::*;
 
-pub mod borrow;
+mod borrow;
 #[allow(unused_imports)]
 pub use borrow::*;
 
-pub mod tuple;
+mod tuple;
 #[allow(unused_imports)]
 pub use tuple::*;
 
-pub mod resource;
+mod resource;
 #[allow(unused_imports)]
 pub use resource::*;
 
-pub mod tick;
+mod tick;
 #[allow(unused_imports)]
 pub use tick::*;
 
-pub mod world;
+mod world;
 #[allow(unused_imports)]
 pub use world::*;
 
@@ -87,11 +87,47 @@ pub trait IntoQuery {
     fn into_query(self) -> Self;
 }
 
+impl<'a> Fetch<'a> for () {
+    type Item = ();
+
+    fn dangling() -> Self {
+        unreachable!()
+    }
+
+    unsafe fn get_item(&mut self, _: ArchetypeEntityId) -> Self::Item {
+        ()
+    }
+}
+
+impl Query for () {
+    type Item<'a> = ();
+
+    type Fetch<'a> = ();
+
+    const ALWAYS_FETCHES: bool = true;
+
+    fn new() -> Self {
+        ()
+    }
+
+    fn can_visit_archetype(&self, _: &Archetype) -> bool {
+        true
+    }
+
+    unsafe fn fetch<'a>(&self, _: &'a World, _: &'a Archetype, _: Tick) -> Self::Fetch<'a> {
+        ()
+    }
+}
+
+impl AsQuery for () {
+    type Query = ();
+}
+
 #[cfg(test)]
 mod tests {
-    use crate::{world::World, archetype::Archetype, tests::Vec2};
+    use crate::{World, archetype::Archetype, tests::Vec2};
 
-    use super::{View, Entities};
+    use super::{ViewState, Entities};
 
     #[test]
     fn simple_view() {
@@ -104,7 +140,7 @@ mod tests {
 
         let archetypes: Vec<&Archetype> = world.archetypes.values().collect();
 
-        let v = View::<Entities>::new(&world, entities, archetypes);
+        let v = ViewState::<Entities, ()>::new(&world, entities, (), archetypes);
 
         for e in v.into_iter() {
             println!("Got entity! {:?}", e);

lyra-ecs/src/query/resource.rs

@@ -1,6 +1,6 @@
 use std::{marker::PhantomData, cell::{Ref, RefMut}};
 
-use crate::{world::World, resource::ResourceObject};
+use crate::{World, resource::ResourceObject};
 
 use super::{Query, Fetch, AsQuery};
 
@@ -192,9 +192,7 @@ impl<'a, T: ResourceObject> AsQuery for ResMut<'a, T> {
 mod tests {
     use std::ops::{Deref, DerefMut};
 
-    use crate::{world::World, tests::{Vec2, Vec3}, query::QueryResourceMut};
-
-    use super::QueryResource;
+    use crate::{query::{Res, ResMut}, tests::{Vec2, Vec3}, World};
 
     struct SomeCounter(u32);
 
@@ -207,7 +205,7 @@ mod tests {
             println!("Added resource");
         }
 
-        let mut res_iter = world.view_iter::<QueryResource<SomeCounter>>();
+        let mut res_iter = world.view_iter::<Res<SomeCounter>>();
         let res = res_iter.next().unwrap();
         let res = res.deref();
         assert_eq!(res.0, 0);
@@ -228,16 +226,16 @@ mod tests {
             println!("Added resource");
         }
 
-        let i = world.view_iter::<(QueryResource<SomeCounter>, &Vec2)>();
+        let i = world.view_iter::<(Res<SomeCounter>, &Vec2)>();
         assert_eq!(i.count(), 3);
-        let i = world.view_iter::<(&Vec2, QueryResource<SomeCounter>)>();
+        let i = world.view_iter::<(&Vec2, Res<SomeCounter>)>();
         assert_eq!(i.count(), 3);
 
-        for (res, e) in world.view_iter::<(QueryResource<SomeCounter>, &Vec2)>() {
+        for (res, e) in world.view_iter::<(Res<SomeCounter>, &Vec2)>() {
             println!("Got res {}! and entity at {:?}", res.deref().0, e);
         }
 
-        let i = world.view_iter::<QueryResource<SomeCounter>>();
+        let i = world.view_iter::<Res<SomeCounter>>();
         assert_eq!(i.count(), 1);
     }
 
@@ -251,14 +249,14 @@ mod tests {
         }
 
         {
-            let mut resmut_iter = world.view_iter::<QueryResourceMut<SomeCounter>>();
+            let mut resmut_iter = world.view_iter::<ResMut<SomeCounter>>();
             let mut resmut = resmut_iter.next().unwrap();
             let resmut = resmut.deref_mut();
             assert_eq!(resmut.0, 0);
             resmut.0 += 20;
         }
 
-        let mut res_iter = world.view_iter::<QueryResource<SomeCounter>>();
+        let mut res_iter = world.view_iter::<Res<SomeCounter>>();
         let res = res_iter.next().unwrap();
         let res = res.deref();
         assert_eq!(res.0, 20);

lyra-ecs/src/query/tick.rs

@@ -1,6 +1,6 @@
 use std::marker::PhantomData;
 
-use crate::{ComponentColumn, Tick, DynTypeId, world::World};
+use crate::{ComponentColumn, Tick, DynTypeId, World};
 
 use super::{Query, Fetch, AsQuery};
 
@@ -90,11 +90,11 @@ where
     }
 
     fn can_visit_archetype(&self, archetype: &crate::archetype::Archetype) -> bool {
-        archetype.columns.iter().any(|c| c.info.type_id == self.type_id)
+        archetype.has_column(self.type_id)
     }
 
     unsafe fn fetch<'a>(&self, _world: &'a World, archetype: &'a crate::archetype::Archetype, _tick: crate::Tick) -> Self::Fetch<'a> {
-        let col = archetype.columns.iter().find(|c| c.info.type_id == self.type_id)
+        let col = archetype.get_column(self.type_id)
             .expect("You ignored 'can_visit_archetype'!");
 
         FetchTickOf {

lyra-ecs/src/query/tuple.rs

@@ -1,7 +1,51 @@
-use crate::world::World;
+use crate::World;
 
 use super::{Query, Fetch, AsQuery};
 
+impl<'a, F1> Fetch<'a> for (F1,)
+where
+    F1: Fetch<'a>,
+{
+    type Item = (F1::Item,);
+
+    fn dangling() -> Self {
+        (F1::dangling(),)
+    }
+
+    fn can_visit_item(&mut self, entity: crate::world::ArchetypeEntityId) -> bool {
+        let (f1,) = self;
+        f1.can_visit_item(entity)
+    }
+    
+    unsafe fn get_item(&mut self, entity: crate::world::ArchetypeEntityId) -> Self::Item {
+        let (f1,) = self;
+        ( f1.get_item(entity), )
+    }
+}
+
+impl<Q1> Query for (Q1,)
+where
+    Q1: Query,
+{
+    type Item<'a> = (Q1::Item<'a>,);
+
+    type Fetch<'a> = (Q1::Fetch<'a>,);
+
+    fn new() -> Self {
+        (Q1::new(),)
+    }
+
+    fn can_visit_archetype(&self, archetype: &crate::archetype::Archetype) -> bool {
+        let (q1,) = self;
+        q1.can_visit_archetype(archetype)
+    }
+
+    unsafe fn fetch<'a>(&self, world: &'a World, archetype: &'a crate::archetype::Archetype, tick: crate::Tick) -> Self::Fetch<'a> {
+        let (q1,) = self;
+        ( q1.fetch(world, archetype, tick), )
+    }
+}
+
 // Technically all of these implementations for a 2-sized tuple
 // can be implemented by the macro near the end of the file, but
 // these are left here for development.
@@ -131,7 +175,7 @@ impl_bundle_tuple! { Q1, Q2, Q3, Q4, Q5, Q6, Q7, Q8, Q9, Q10, Q11, Q12, Q13, Q14
 
 #[cfg(test)]
 mod tests {
-    use crate::{world::World, tests::{Vec2, Vec3}};
+    use crate::{World, tests::{Vec2, Vec3}};
 
     #[test]
     fn tuple_queries() {

lyra-ecs/src/query/view.rs

@@ -4,41 +4,64 @@ use crate::{archetype::Archetype, world::{ArchetypeEntityId, World}, EntityId, T
 
 use super::{Query, Fetch, AsQuery};
 
-pub struct View<'a, Q: AsQuery> {
+pub type View<'a, Q, F = ()> = ViewState<'a, <Q as AsQuery>::Query, <F as AsQuery>::Query>;
+
+pub struct ViewState<'a, Q: Query, F: Query> {
     world: &'a World,
-    query: Q::Query,
+    query: Q,
+    filter: F,
     archetypes: Vec<&'a Archetype>,
 }
 
-impl<'a, Q> View<'a, Q>
+impl<'a, Q, F> ViewState<'a, Q, F>
 where
-    Q: AsQuery,
+    Q: Query,
+    F: Query,
 {
-    pub fn new(world: &'a World, query: Q::Query, archetypes: Vec<&'a Archetype>) -> Self {
+    pub fn new(world: &'a World, query: Q, filter: F, archetypes: Vec<&'a Archetype>) -> Self {
         Self {
             world,
             query,
+            filter,
             archetypes,
         }
     }
+
+    /// Converts self into an iterator
+    pub fn iter(self) -> ViewIter<'a, Q, F> {
+        self.into_iter()
+    }
+
+    /// Consumes `self`, adding a query to the view.
+    pub fn expand<U: AsQuery>(self, query: U::Query) -> ViewState<'a, (Q, U::Query), F> {
+        ViewState::new(self.world, (self.query, query), self.filter, self.archetypes)
+    }
+
+    /// Consumes `self`, adding a filter to the view.
+    pub fn with<U: AsQuery>(self, filter: U::Query) -> ViewState<'a, Q, (F, U::Query)> {
+        ViewState::new(self.world, self.query, (self.filter, filter), self.archetypes)
+    }
 }
 
-impl<'a, Q> IntoIterator for View<'a, Q>
+impl<'a, Q, F> IntoIterator for ViewState<'a, Q, F>
 where
-    Q: AsQuery,
+    Q: Query,
+    F: Query,
 {
-    type Item = <Q::Query as Query>::Item<'a>;
+    type Item = Q::Item<'a>;
 
-    type IntoIter = ViewIter<'a, Q::Query>;
+    type IntoIter = ViewIter<'a, Q, F>;
 
     fn into_iter(self) -> Self::IntoIter {
-        let tick = self.world.tick_tracker().tick_when(Q::Query::MUTATES);
+        let tick = self.world.tick_tracker().tick_when(Q::MUTATES);
 
         ViewIter {
             world: self.world,
             tick,
             query: self.query,
+            filter: self.filter,
             fetcher: None,
+            filter_fetcher: None,
             archetypes: self.archetypes,
             next_archetype: 0,
             component_indices: 0..0,
@@ -46,25 +69,28 @@ where
     }
 }
 
-pub struct ViewIter<'a, Q: Query> {
+pub struct ViewIter<'a, Q: Query, F: Query> {
     world: &'a World,
     tick: Tick,
     query: Q,
+    filter: F,
     fetcher: Option<Q::Fetch<'a>>,
+    filter_fetcher: Option<F::Fetch<'a>>,
     archetypes: Vec<&'a Archetype>,
     next_archetype: usize,
     component_indices: Range<u64>,
 }
 
-impl<'a, Q> Iterator for ViewIter<'a, Q>
+impl<'a, Q, F> Iterator for ViewIter<'a, Q, F>
 where
     Q: Query,
+    F: Query,
 {
     type Item = Q::Item<'a>;
 
     fn next(&mut self) -> Option<Self::Item> {
         loop {
-            if Q::ALWAYS_FETCHES {
+            if Q::ALWAYS_FETCHES && F::ALWAYS_FETCHES {
                 // only fetch this query once.
                 // fetcher gets set to Some after this `next` call.
                 if self.fetcher.is_none() {
@@ -80,10 +106,10 @@ where
 
             if let Some(entity_index) = self.component_indices.next() {
                 let fetcher = self.fetcher.as_mut().unwrap();
+                let filter_fetcher = self.filter_fetcher.as_mut().unwrap();
                 let entity_index = ArchetypeEntityId(entity_index);
-                if !fetcher.can_visit_item(entity_index) {
-                    continue;
-                } else {
+
+                if fetcher.can_visit_item(entity_index) && filter_fetcher.can_visit_item(entity_index) {
                     let i = unsafe { fetcher.get_item(entity_index) };
                     return Some(i);
                 }
@@ -96,16 +122,17 @@ where
                 self.next_archetype += 1;
                 let arch = unsafe { self.archetypes.get_unchecked(arch_id) };
 
-                if arch.entities.is_empty() {
+                if arch.entity_ids.is_empty() {
                     continue;
                 }
 
-                if !self.query.can_visit_archetype(arch) {
-                    continue;
+                if self.query.can_visit_archetype(arch) && self.filter.can_visit_archetype(arch) {
+                    unsafe {
+                        self.fetcher = Some(self.query.fetch(self.world, arch, self.tick));
+                        self.filter_fetcher = Some(self.filter.fetch(self.world, arch, self.tick));
+                    }
+                    self.component_indices = 0..arch.entity_ids.len() as u64;
                 }
-
-                self.fetcher = unsafe { Some(self.query.fetch(self.world, arch, self.tick)) };
-                self.component_indices = 0..arch.entities.len() as u64;
             }
         }
     }

lyra-ecs/src/relation/mod.rs

@@ -0,0 +1,177 @@
+use std::marker::PhantomData;
+
+use lyra_ecs_derive::Component;
+
+use crate::query::Query;
+use crate::query::ViewState;
+use crate::Entity;
+
+use crate::lyra_engine;
+use crate::World;
+
+mod relates_to;
+#[doc(hidden)]
+pub use relates_to::*;
+
+mod relate_pair;
+#[doc(hidden)]
+pub use relate_pair::*;
+
+#[allow(unused_variables)]
+pub trait Relation: 'static {
+    /// called when a relation of this type is set on a target
+    fn relation_add(&self, origin: Entity, target: Entity) { }
+    /// called when a relation is removed
+    fn relation_remove(&self, origin: Entity, target: Entity) { }
+}
+
+/// A component that stores the target of a relation.
+/// 
+/// This component is on the origin of the relation and can be used to find all 
+/// entities that the relation targets.
+#[derive(Component)]
+pub struct RelationOriginComponent<R: Relation> {
+    pub(crate) relation: R,
+    target: Entity,
+}
+
+/// A component that stores the origin of a relation.
+/// 
+/// This component is on the target of the relation and can be used to find the
+/// origin of the relation -- the entity that targets this entity.
+#[derive(Component)]
+pub struct RelationTargetComponent<R: Relation> {
+    #[allow(dead_code)]
+    origin: Entity,
+    _marker: PhantomData<R>,
+}
+
+impl World {
+    /// Creates a relation between two entities. 
+    /// 
+    /// ```nobuild
+    /// struct ChildOf;
+    /// 
+    /// impl Relation for ChildOf { /* snip */ };
+    /// 
+    /// let a = world.spawn((Vec2 { x: 10.0, y: 20.0 },));
+    /// let b = world.spawn((Vec2 { x: 158.0, y: 65.0 },));
+    /// 
+    /// // Entity a is a child of entity b
+    /// world.add_relation(a, ChildOf, b);
+    /// 
+    /// // Construct a view for querying the entities that have a relation to entity `b`.
+    /// let v = world.view::<Entities>()
+    ///     .relates_to::<ChildOf>(b);
+    /// 
+    /// // Iterate through the entities. ChildOf has no members, so it will be unused.
+    /// for (e, _childof) in v.into_iter() {
+    ///     println!("{:?} is a child of {:?}", e, b);
+    /// }
+    /// ```
+    pub fn add_relation<R>(&mut self, origin: Entity, relation: R, target: Entity)
+    where
+        R: Relation
+    {
+        let comp = RelationTargetComponent {
+            origin,
+            _marker: PhantomData::<R>,
+        };
+        self.insert(target, comp);
+
+        let comp = RelationOriginComponent {
+            relation,
+            target,
+        };
+        
+        comp.relation.relation_add(origin, target);
+        self.insert(origin, comp);
+    }
+}
+impl<'a, Q, F> ViewState<'a, Q, F>
+where
+    Q: Query,
+    F: Query,
+{
+    /// Consumes `self` to return a view that fetches the relation to a specific target entity.
+    pub fn relates_to<R>(self, target: Entity) -> ViewState<'a, (Q, QueryRelatesTo<R>), F>
+    where
+        R: Relation,
+    {
+        let rel = QueryRelatesTo::new(Some(target));
+        self.expand::<RelatesTo<R>>(rel)
+    }
+
+    /// Consumes `self` to return a view that fetches the origin, target, and a reference to
+    /// the relation that the entities have together.
+    pub fn relate_pair<R>(self) -> ViewState<'a, (Q, QueryRelatePair<R>), F>
+    where
+        R: Relation,
+    {
+        let rel = QueryRelatePair::<R>::new();
+        self.expand::<RelatePair<R>>(rel)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::{query::{Entities, ViewState}, relation::QueryRelatesTo, tests::Vec2, World};
+
+    use super::{RelatePair, Relation};
+
+    struct ChildOf;
+
+    impl Relation for ChildOf {
+
+    }
+
+    #[test]
+    fn simple_relates_to() {
+        let mut world = World::new();
+
+        let a = world.spawn((Vec2::new(10.0, 20.0),));
+        let b = world.spawn((Vec2::new(158.0, 65.0),));
+
+        world.add_relation(a, ChildOf, b);
+
+        let archetypes = world.archetypes.values().collect();
+        let v = ViewState::<(Entities, QueryRelatesTo<ChildOf>), ()>::new(&world, (Entities::default(), QueryRelatesTo::new(Some(b))), (), archetypes);
+
+        for (e, _relation) in v.into_iter() {
+            println!("{:?} is a child of {:?}", e, b);
+        };
+    }
+
+    #[test]
+    fn simple_relates_to_view() {
+        let mut world = World::new();
+
+        let a = world.spawn((Vec2::new(10.0, 20.0),));
+        let b = world.spawn((Vec2::new(158.0, 65.0),));
+
+        world.add_relation(a, ChildOf, b);
+
+        let v = world.view::<Entities>()
+            .relates_to::<ChildOf>(b);
+
+        for (e, _rel) in v.into_iter() {
+            println!("{:?} is a child of {:?}", e, b);
+        }
+    }
+
+    #[test]
+    fn simple_relate_pair_view() {
+        let mut world = World::new();
+
+        let a = world.spawn((Vec2::new(10.0, 20.0),));
+        let b = world.spawn((Vec2::new(158.0, 65.0),));
+
+        world.add_relation(a, ChildOf, b);
+
+        let v = world.view::<RelatePair<ChildOf>>();
+
+        for (origin, _childof, target) in v.into_iter() {
+            println!("{:?} is a child of {:?}", origin, target);
+        }
+    }
+}

lyra-ecs/src/relation/relate_pair.rs

@@ -0,0 +1,94 @@
+use std::{any::{Any, TypeId}, cell::Ref, marker::PhantomData};
+
+use crate::{query::{AsQuery, Fetch, Query}, Archetype, ComponentColumn, Entity, World};
+
+use super::{Relation, RelationOriginComponent};
+
+pub struct FetchRelatePair<'a, T> {
+    col: &'a ComponentColumn,
+    arch: &'a Archetype,
+    _phantom: PhantomData<&'a T>
+}
+
+impl<'a, R> Fetch<'a> for FetchRelatePair<'a, R>
+where
+    R: Relation,
+{
+    type Item = (Entity, Ref<'a, R>, Entity);
+
+    fn dangling() -> Self {
+        unreachable!()
+    }
+
+    unsafe fn get_item(&mut self, entity: crate::world::ArchetypeEntityId) -> Self::Item {
+        let comp: Ref<RelationOriginComponent<R>> = self.col.get(entity.0 as usize);
+        let rel_target = comp.target;
+        let rel_origin = self.arch.entity_at_index(entity).unwrap();
+
+        let comp = Ref::map(comp, |r| &r.relation);
+        (rel_origin, comp, rel_target)
+    }
+}
+
+pub struct QueryRelatePair<R> {
+    _marker: PhantomData<R>,
+}
+
+impl<R> Copy for QueryRelatePair<R> {}
+
+impl<R> Clone for QueryRelatePair<R> {
+    fn clone(&self) -> Self {
+        *self
+    }
+}
+
+impl<R> QueryRelatePair<R> {
+    pub fn new() -> Self {
+        Self {
+            _marker: PhantomData
+        }
+    }
+}
+
+impl<R> Query for QueryRelatePair<R>
+where
+    R: Relation + 'static
+{
+    type Item<'a> = (Entity, Ref<'a, R>, Entity);
+
+    type Fetch<'a> = FetchRelatePair<'a, R>;
+
+    fn new() -> Self {
+        QueryRelatePair::<R>::new()
+    }
+
+    fn can_visit_archetype(&self, archetype: &crate::archetype::Archetype) -> bool {
+        let tyid = crate::DynTypeId::Rust(TypeId::of::<RelationOriginComponent<R>>());
+        archetype.has_column(tyid)
+    }
+
+    unsafe fn fetch<'a>(&self, _world: &'a World, archetype: &'a crate::archetype::Archetype, tick: crate::Tick) -> Self::Fetch<'a> {
+        let _ = tick;
+        let col = archetype.get_column(self.type_id())
+            .expect("You ignored 'can_visit_archetype'!");
+
+        FetchRelatePair {
+            col,
+            arch: archetype,
+            _phantom: PhantomData,
+        }
+    }
+}
+
+/// A query that fetches the origin, and target of a relation of type `R`.
+/// 
+/// It provides it as a tuple in the following format: `(origin, relation, target)`.
+/// Similar to [`RelatesTo`](super::RelatesTo), you can use [`ViewState::relate_pair`] to get a view that fetches the
+/// pair, or unlike [`RelatesTo`](super::RelatesTo), you can do the common procedure of using [`World::view`].
+pub struct RelatePair<R: Relation> {
+    _marker: PhantomData<R>,
+}
+
+impl<R: Relation> AsQuery for RelatePair<R> {
+    type Query = QueryRelatePair<R>;
+}

lyra-ecs/src/relation/relates_to.rs

@@ -0,0 +1,109 @@
+use std::{any::TypeId, cell::Ref, marker::PhantomData};
+
+use crate::{query::{AsQuery, Fetch, Query}, ComponentColumn, Entity, World};
+
+use super::{Relation, RelationOriginComponent};
+
+pub struct FetchRelatesTo<'a, T> {
+    col: &'a ComponentColumn,
+    target: Entity,
+    _phantom: PhantomData<&'a T>
+}
+
+impl<'a, R> Fetch<'a> for FetchRelatesTo<'a, R>
+where
+    R: Relation,
+{
+    type Item = Ref<'a, R>;
+
+    fn dangling() -> Self {
+        unreachable!()
+    }
+
+    fn can_visit_item(&mut self, entity: crate::ArchetypeEntityId) -> bool {
+        unsafe {
+            let comp: Ref<RelationOriginComponent<R>> = self.col.get(entity.0 as usize);
+            comp.target == self.target
+        }
+    }
+
+    unsafe fn get_item(&mut self, entity: crate::world::ArchetypeEntityId) -> Self::Item {
+        let comp: Ref<RelationOriginComponent<R>> = self.col.get(entity.0 as usize);
+        let comp = Ref::map(comp, |r| &r.relation);
+        comp
+    }
+}
+
+pub struct QueryRelatesTo<R> {
+    target: Option<Entity>,
+    _marker: PhantomData<R>,
+}
+
+impl<R> Copy for QueryRelatesTo<R> {}
+
+impl<R> Clone for QueryRelatesTo<R> {
+    fn clone(&self) -> Self {
+        *self
+    }
+}
+
+impl<R> QueryRelatesTo<R> {
+    pub fn new(target: Option<Entity>) -> Self {
+        Self {
+            target,
+            _marker: PhantomData
+        }
+    }
+}
+
+impl<R> Query for QueryRelatesTo<R>
+where
+    R: Relation + 'static
+{
+    type Item<'a> = Ref<'a, R>;
+
+    type Fetch<'a> = FetchRelatesTo<'a, R>;
+
+    fn new() -> Self {
+        panic!("RelatesTo MUST be made with View::relates_to since it requires State provided by \
+            that function.")
+    }
+
+    fn can_visit_archetype(&self, archetype: &crate::archetype::Archetype) -> bool {
+        archetype.has_column(TypeId::of::<RelationOriginComponent<R>>())
+    }
+
+    unsafe fn fetch<'a>(&self, _world: &'a World, archetype: &'a crate::archetype::Archetype, tick: crate::Tick) -> Self::Fetch<'a> {
+        let _ = tick;
+        let col = archetype.get_column(TypeId::of::<RelationOriginComponent<R>>())
+            .expect("You ignored 'can_visit_archetype'!");
+
+        FetchRelatesTo {
+            col,
+            target: self.target.expect("Filter not initialized"),
+            _phantom: PhantomData,
+        }
+    }
+}
+
+/// A query that fetches the relation to a specific target entity.
+/// 
+/// This can be combined with Entities, to query all entities that have a relation targeting
+/// the target entity.
+/// 
+/// ```nobuild
+/// let v = world.view::<Entities>()
+///     .relates_to::<ChildOf>(b);
+/// 
+/// // Iterate through the entities. ChildOf has no members, so it will be unused.
+/// for (e, _childof) in v.into_iter() {
+///     println!("{:?} is a child of {:?}", e, b);
+/// }
+/// ```
+pub struct RelatesTo<R: Relation> {
+    _marker: PhantomData<R>,
+}
+
+impl<R: Relation> AsQuery for RelatesTo<R> {
+    type Query = QueryRelatesTo<R>;
+}

lyra-ecs/src/system/batched.rs

@@ -1,4 +1,4 @@
-use lyra_ecs::world::World;
+use lyra_ecs::World;
 
 use crate::Access;
 

lyra-ecs/src/system/criteria.rs

@@ -1,15 +1,24 @@
 use std::ptr::NonNull;
 
-use lyra_ecs::world::World;
+use lyra_ecs::World;
 
+/// An enum that is used to control if the Criteria was met or not.
 #[derive(Clone, Copy, Debug, Hash, PartialEq, Eq, PartialOrd, Ord)]
 pub enum CriteriaSchedule {
+    /// The criteria was completely met and the system can continue to run.
     Yes,
+    /// The criteria was not met and must run next time the system batch is ran.
     No,
+    /// The criteria was met and the system can run.
+    /// After the system runs, the criteria should be checked again and may cause another
+    /// execution of the system.
     YesAndLoop,
+    /// The criteria was not met, but it should be checked again during this tick before giving
+    /// up. If the criteria returns `Yes` next check, the systems will run.
     NoAndLoop,
 }
 
+/// A Criteria can be used to conditionally execute [`BatchedSystem`](super::BatchedSystem).
 pub trait Criteria {
     /// Checks if this Criteria can run, and if it should check it again.
     /// 

lyra-ecs/src/system/fn_sys.rs

@@ -1,10 +1,11 @@
 use std::{any::Any, marker::PhantomData, ptr::NonNull};
 
 use paste::paste;
-use crate::{world::World, Access, ResourceObject, query::{Query, View, AsQuery, ResMut, Res}};
+use crate::{World, Access, ResourceObject, query::{Query, ViewState, ResMut, Res}};
 
 use super::{System, IntoSystem};
 
+/// A trait that is used for fetching an argument for a [`FnSystem`].
 pub trait FnArgFetcher {
     /// stores data that persists after an execution of a system
     type State: 'static;
@@ -30,14 +31,20 @@ pub trait FnArgFetcher {
     fn apply_deferred(state: Self::State, world: NonNull<World>);
 }
 
-pub trait FnArg {
-    type Fetcher: FnArgFetcher;
-}
-
+/// A system that is implemented as a function.
+/// 
+/// The arguments of the functions must implement `FnArgFetcher` so that the arguments can be
+/// fetched on the fly.
+/// 
+/// ```fail_compile
+/// fn enemy_movement_system(enemies: View<(&Health, &EnemyStats, &Movement)>) -> anyhow::Result<()> {
+///     for (health, stats, movement) in enemies.iter() {
+///         // ...
+///     }
+/// }
+/// ```
 pub struct FnSystem<F, Args> {
     inner: F,
-    //#[allow(dead_code)]
-    //args: Args,
     arg_state: Option<Vec<Box<dyn Any>>>,
     _marker: PhantomData<Args>,
 }
@@ -129,22 +136,14 @@ impl_fn_system_tuple!{ A, B, C, D, E, F2, G, H, I, J, K, L, M, N }
 impl_fn_system_tuple!{ A, B, C, D, E, F2, G, H, I, J, K, L, M, N, O }
 impl_fn_system_tuple!{ A, B, C, D, E, F2, G, H, I, J, K, L, M, N, O, P }
 
-/// An ArgFetcher implementation for query [`View`]s
-/* pub struct ViewArgFetcher<Q: AsQuery> {
-    query: Q::Query
-}
-
-impl<'a, Q: AsQuery> FnArg for View<'a, Q> {
-    type Fetcher = ViewArgFetcher<Q>;
-} */
-
-impl<'c, Q> FnArgFetcher for View<'c, Q>
+/// An ArgFetcher implementation for query [`ViewState`]s
+impl<'c, Q, F> FnArgFetcher for ViewState<'c, Q, F>
 where
-    Q: AsQuery,
-    <Q as AsQuery>::Query: 'static
+    Q: Query + 'static,
+    F: Query + 'static,
 {
-    type State = Q::Query;
-    type Arg<'a, 'state> = View<'a, Q>;
+    type State = (Q, F);
+    type Arg<'a, 'state> = ViewState<'a, Q, F>;
 
     fn world_access(&self) -> Access {
         todo!()
@@ -153,7 +152,8 @@ where
     unsafe fn get<'a, 'state>(state: &'state mut Self::State, world: NonNull<World>) -> Self::Arg<'a, 'state> {
         let world = &*world.as_ptr();
         let arch = world.archetypes.values().collect();
-        let v = View::new(world, state.clone(), arch);
+        let (query, filter) = state.clone();
+        let v = ViewState::new(world, query, filter, arch);
 
         v
     }
@@ -161,17 +161,10 @@ where
     fn apply_deferred(_: Self::State, _: NonNull<World>) { }
     
     fn create_state(_: NonNull<World>) -> Self::State { 
-        <Q::Query as Query>::new()
+        (Q::new(), F::new())
     }
 }
 
-/// An ArgFetcher implementation for borrowing the [`World`].
-/* pub struct WorldArgFetcher;
-
-impl<'a> FnArg for &'a World {
-    type Fetcher = WorldArgFetcher;
-} */
-
 impl FnArgFetcher for &'_ World {
     type State = ();
     type Arg<'a, 'state> = &'a World;
@@ -246,7 +239,7 @@ impl<R: ResourceObject> FnArgFetcher for ResMut<'_, R> {
 mod tests {
     use std::ptr::NonNull;
 
-    use crate::{tests::{Vec2, Vec3}, world::World, query::{QueryBorrow, View, ResMut}};
+    use crate::{tests::{Vec2, Vec3}, World, query::{QueryBorrow, ViewState, ResMut}};
     use super::{System, IntoSystem};
 
     struct SomeCounter(u32);
@@ -262,7 +255,7 @@ mod tests {
 
         let mut count = 0;
 
-        let test_system = |view: View<QueryBorrow<Vec2>>| -> anyhow::Result<()> {
+        let test_system = |view: ViewState<QueryBorrow<Vec2>, ()>| -> anyhow::Result<()> {
             let mut vecs = vecs.to_vec();
             for v in view.into_iter() {
                 let pos = vecs.iter().position(|vec| *vec == *v)
@@ -291,7 +284,7 @@ mod tests {
 
         let mut count = 0;
 
-        let test_system = |view: View<(QueryBorrow<Vec2>, QueryBorrow<Vec3>)>| -> anyhow::Result<()> {
+        let test_system = |view: ViewState<(QueryBorrow<Vec2>, QueryBorrow<Vec3>), ()>| -> anyhow::Result<()> {
             for (v2, v3) in view.into_iter() {
                 println!("Got v2 at '{:?}' and v3 at: '{:?}'", v2, v3);
                 count += 1;
@@ -392,7 +385,7 @@ mod tests {
         world.spawn((Vec2::rand(), ));
         world.add_resource(SomeCounter(0));
 
-        let test_system = |mut counter: ResMut<SomeCounter>, view: View<QueryBorrow<Vec2>>| -> anyhow::Result<()> {
+        let test_system = |mut counter: ResMut<SomeCounter>, view: ViewState<QueryBorrow<Vec2>, ()>| -> anyhow::Result<()> {
             for v2 in view.into_iter() {
                 println!("Got v2 at '{:?}'", v2);
                 // .0 is twice here since ResMut's tuple field is pub(crate).

lyra-ecs/src/system/graph.rs

@@ -2,7 +2,7 @@ use std::{collections::{HashMap, VecDeque, HashSet}, ptr::NonNull};
 
 use super::System;
 
-use crate::{world::World, CommandQueue, Commands};
+use crate::{World, CommandQueue, Commands};
 
 #[derive(thiserror::Error, Debug)]
 pub enum GraphExecutorError {
@@ -140,7 +140,7 @@ impl GraphExecutor {
 mod tests {
     use std::ptr::NonNull;
 
-    use crate::{world::World, query::{ResMut, View}, system::IntoSystem};
+    use crate::{query::{ResMut, View}, system::IntoSystem, World};
 
     use super::GraphExecutor;
 
@@ -152,7 +152,7 @@ mod tests {
 
         let mut exec = GraphExecutor::new();
 
-        let a_system = |view: View<ResMut<Vec<String>>>| -> anyhow::Result<()> {
+        let a_system = |view: View<ResMut<Vec<String>>, ()>| -> anyhow::Result<()> {
             println!("System 'a' ran!");
             
             let mut order = view.into_iter().next().unwrap();
@@ -161,7 +161,7 @@ mod tests {
             Ok(())
         };
 
-        let b_system = |view: View<ResMut<Vec<String>>>| -> anyhow::Result<()> {
+        let b_system = |view: View<ResMut<Vec<String>>, ()>| -> anyhow::Result<()> {
             println!("System 'b' ran!");
 
             let mut order = view.into_iter().next().unwrap();
@@ -170,7 +170,7 @@ mod tests {
             Ok(())
         };
 
-        let c_system = |view: View<ResMut<Vec<String>>>| -> anyhow::Result<()> {
+        let c_system = |view: View<ResMut<Vec<String>>, ()>| -> anyhow::Result<()> {
             println!("System 'c' ran!");
 
             let mut order = view.into_iter().next().unwrap();

lyra-ecs/src/system/mod.rs

@@ -1,17 +1,17 @@
 use std::ptr::NonNull;
 
-use crate::{world::World, Access};
+use crate::{World, Access};
 
-pub mod graph;
+mod graph;
 pub use graph::*;
 
-pub mod criteria;
+mod criteria;
 pub use criteria::*;
 
-pub mod batched;
+mod batched;
 pub use batched::*;
 
-pub mod fn_sys;
+mod fn_sys;
 pub use fn_sys::*;
 
 /// A system that does not mutate the world

lyra-ecs/src/tick.rs

@@ -1,9 +1,9 @@
 use std::sync::atomic::{AtomicU64, Ordering};
 
-/// TickTracker is used for tracking changes of [`Component`]s and entities.
+/// TickTracker is used for tracking changes of [`Component`](crate::Component)s and entities.
 /// 
 /// TickTracker stores an [`AtomicU64`], making all operations on `TickTracker`, atomic as well.
-/// Note that [`Tick::Clone`] only clones the inner value of atomic, and not the atomic itself.
+/// Note that [`Tick::clone`] only clones the inner value of atomic, and not the atomic itself.
 #[derive(Debug, Default)]
 pub struct TickTracker {
     tick: AtomicU64,

lyra-ecs/src/world.rs

@@ -1,9 +1,10 @@
 use std::{any::TypeId, cell::{Ref, RefMut}, collections::HashMap, ptr::NonNull};
 
-use crate::{archetype::{Archetype, ArchetypeId}, bundle::Bundle, query::{dynamic::DynamicView, AsQuery, Query, View, ViewIter, ViewOne}, resource::ResourceData, ComponentInfo, DynTypeId, Entities, Entity, ResourceObject, Tick, TickTracker};
+use crate::{archetype::{Archetype, ArchetypeId}, bundle::Bundle, query::{dynamic::DynamicView, AsQuery, Query, ViewState, ViewIter, ViewOne}, resource::ResourceData, ComponentInfo, DynTypeId, Entities, Entity, ResourceObject, Tick, TickTracker};
 
 /// The id of the entity for the Archetype.
-/// The Archetype struct uses this as the index in the component columns
+/// 
+/// The Archetype uses this as the index in the component columns
 #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
 pub struct ArchetypeEntityId(pub u64);
 
@@ -53,7 +54,7 @@ impl World {
     }
 
     /// Spawn the components into a reserved entity. Only do this with entities that
-    /// were 'reserved' with [`World::reserve`]
+    /// were reserved with [`World::reserve_entity`].
     ///
     /// # Safety
     /// Do not use this method with an entity that is currently alive, it WILL cause undefined behavior.
@@ -72,14 +73,14 @@ impl World {
 
         if let Some(archetype) = archetype {
             // make at just one check to ensure you're not spawning twice
-            debug_assert!(!archetype.entities.contains_key(&entity),
+            debug_assert!(!archetype.entity_ids.contains_key(&entity),
                 "You attempted to spawn components into an entity that already exists!");
 
             let arche_idx = archetype.add_entity(entity, bundle, &tick);
 
             // Create entity record and store it
             let record = Record {
-                id: archetype.id,
+                id: archetype.id(),
                 index: arche_idx,
             };
             
@@ -142,7 +143,7 @@ impl World {
         let record = self.entities.entity_record(entity).unwrap();
         let current_arch = self.archetypes.get(&record.id).unwrap();
         
-        let mut col_types: Vec<DynTypeId> = current_arch.columns.iter().map(|c| c.info.type_id).collect();
+        let mut col_types: Vec<DynTypeId> = current_arch.columns.iter().map(|c| c.info.type_id()).collect();
         let orig_col = col_types.clone();
         col_types.extend(bundle.type_ids());
         
@@ -157,7 +158,7 @@ impl World {
             for (col_type, (col_ptr, col_info)) in orig_col.into_iter().zip(col_ptrs.into_iter()) {
                 unsafe {
                     let ptr = NonNull::new_unchecked(col_ptr.as_ptr()
-                        .add(res_index.0 as usize * col_info.layout.size));
+                        .add(res_index.0 as usize * col_info.layout().size()));
                     let col = arch.get_column_mut(col_type).unwrap();
                     col.set_at(res_index.0 as _, ptr, tick);
                 }
@@ -169,10 +170,10 @@ impl World {
                 col.len += 1;
             });
 
-            arch.entities.insert(entity, res_index);
+            arch.entity_ids.insert(entity, res_index);
             
             let new_record = Record {
-                id: arch.id,
+                id: arch.id(),
                 index: res_index,
             };
             self.entities.insert_entity_record(entity, new_record);
@@ -207,9 +208,20 @@ impl World {
     }
 
     /// View into the world for a set of entities that satisfy the queries.
-    pub fn view_iter<T: 'static + AsQuery>(&self) -> ViewIter<T::Query> {
+    pub fn view<Q: AsQuery>(&self) -> ViewState<Q::Query, ()> {
+        self.filtered_view::<Q, ()>()
+    }
+
+    /// View into the world for a set of entities that satisfy the query and the filter.
+    pub fn filtered_view<Q: AsQuery, F: AsQuery>(&self) -> ViewState<Q::Query, F::Query> {
         let archetypes = self.archetypes.values().collect();
-        let v = View::<T>::new(self, T::Query::new(), archetypes);
+        ViewState::<Q::Query, F::Query>::new(self, Q::Query::new(), F::Query::new(), archetypes)
+    }
+
+    /// View into the world for a set of entities that satisfy the queries.
+    pub fn view_iter<Q: AsQuery>(&self) -> ViewIter<Q::Query, ()> {
+        let archetypes = self.archetypes.values().collect();
+        let v = ViewState::new(self, Q::Query::new(), (), archetypes);
         v.into_iter()
     }
 
@@ -217,7 +229,7 @@ impl World {
         DynamicView::new(self)
     }
 
-    pub fn view_one<T: 'static + AsQuery>(&self, entity: Entity) -> ViewOne<T::Query> {
+    pub fn view_one<T: AsQuery>(&self, entity: Entity) -> ViewOne<T::Query> {
         ViewOne::new(self, entity.id, T::Query::new())
     }
 
@@ -252,7 +264,7 @@ impl World {
 
     /// Gets a resource from the World.
     /// 
-    /// Will panic if the resource is not in the world. See [`try_get_resource`] for
+    /// Will panic if the resource is not in the world. See [`World::try_get_resource`] for
     /// a function that returns an option.
     pub fn get_resource<T: 'static>(&self) -> Ref<T> {
         self.resources.get(&TypeId::of::<T>())
@@ -275,7 +287,7 @@ impl World {
 
     /// Gets a mutable borrow of a resource from the World.
     /// 
-    /// Will panic if the resource is not in the world. See [`try_get_resource_mut`] for
+    /// Will panic if the resource is not in the world. See [`World::try_get_resource_mut`] for
     /// a function that returns an option.
     pub fn get_resource_mut<T: 'static>(&self) -> RefMut<T> {
         self.resources.get(&TypeId::of::<T>())

lyra-game/src/delta_time.rs

@@ -1,5 +1,5 @@
 use instant::Instant;
-use lyra_ecs::{Component, world::World};
+use lyra_ecs::{Component, World};
 use lyra_reflect::Reflect;
 
 use crate::{plugin::Plugin, game::GameStages};

lyra-game/src/game.rs

@@ -2,7 +2,7 @@ use std::{sync::Arc, collections::VecDeque, ptr::NonNull};
 
 use async_std::task::block_on;
 
-use lyra_ecs::{world::World, system::{System, IntoSystem}};
+use lyra_ecs::{World, system::{System, IntoSystem}};
 use tracing::{info, error, Level};
 use tracing_appender::non_blocking;
 use tracing_subscriber::{

lyra-game/src/input/action.rs

@@ -1,7 +1,7 @@
 use std::{collections::HashMap, ops::Deref, hash::{Hash, DefaultHasher, Hasher}, fmt::Debug};
 
 use glam::Vec2;
-use lyra_ecs::world::World;
+use lyra_ecs::World;
 use lyra_reflect::Reflect;
 
 use crate::{plugin::Plugin, game::GameStages, EventQueue};

lyra-game/src/input/system.rs

@@ -1,7 +1,7 @@
 use std::ptr::NonNull;
 
 use glam::Vec2;
-use lyra_ecs::{world::World, system::IntoSystem};
+use lyra_ecs::{World, system::IntoSystem};
 use winit::event::MouseScrollDelta;
 
 use crate::{EventQueue, plugin::Plugin, game::GameStages};

lyra-game/src/render/light/mod.rs

@@ -2,7 +2,7 @@ pub mod point;
 pub mod directional;
 pub mod spotlight;
 
-use lyra_ecs::{Entity, Tick, world::World, query::{Entities, TickOf}};
+use lyra_ecs::{Entity, Tick, World, query::{Entities, TickOf}};
 pub use point::*;
 pub use spotlight::*;
 

lyra-game/src/render/renderer.rs

@@ -7,7 +7,7 @@ use instant::Instant;
 use itertools::izip;
 use lyra_ecs::Entity;
 use lyra_ecs::query::{Entities, TickOf};
-use lyra_ecs::world::World;
+use lyra_ecs::World;
 use tracing::{debug, warn};
 use wgpu::{BindGroupLayout, Limits};
 use wgpu::util::DeviceExt;

lyra-game/src/render/window.rs

@@ -1,7 +1,7 @@
 use std::sync::Arc;
 
 use glam::{Vec2, IVec2};
-use lyra_ecs::world::World;
+use lyra_ecs::World;
 use tracing::{warn, error};
 use winit::{window::{Window, Fullscreen}, dpi::{LogicalPosition, LogicalSize, PhysicalPosition}, error::ExternalError};
 

lyra-reflect/src/lib.rs

@@ -2,7 +2,7 @@
 
 use std::{any::TypeId, any::Any, cell::{Ref, RefMut}};
 
-use lyra_ecs::{world::World, DynamicBundle, Component, Entity, ComponentInfo};
+use lyra_ecs::World;
 
 extern crate self as lyra_reflect;
 

lyra-resource/src/loader/model.rs

@@ -62,6 +62,8 @@ impl ModelLoader {
 
     fn process_node(buffers: &Vec<Vec<u8>>, materials: &Vec<Material>, node: gltf::Node<'_>) -> Vec<Mesh> {
         let mut meshes = vec![];
+        //node.transform()
+
         if let Some(mesh) = node.mesh() {
             for prim in mesh.primitives() {
                 let reader = prim.reader(|buf| Some(buffers[buf.index()].as_slice()));

lyra-scripting/src/lua/dynamic_iter.rs

@@ -27,7 +27,7 @@ impl<'a> Fetch<'a> for FetchDynamicType {
     unsafe fn get_item(&mut self, entity: ArchetypeEntityId) -> Self::Item {
         let ptr = unsafe { self.col.as_ref().borrow_ptr() };
         let ptr = NonNull::new_unchecked(ptr.as_ptr()
-            .add(entity.0 as usize * self.info.layout.size));
+            .add(entity.0 as usize * self.info.layout().size()));
 
         DynamicType {
             info: self.info,
@@ -96,7 +96,7 @@ impl Iterator for DynamicViewIter {
                 }
                 
                 let arch = unsafe { self.archetypes.get_unchecked(self.next_archetype - 1).as_ref() };
-                let entity = arch.entity_of_index(entity_index).unwrap();
+                let entity = arch.entity_at_index(entity_index).unwrap();
                 let row = DynamicViewRow {
                     entity,
                     item: fetch_res,
@@ -112,7 +112,7 @@ impl Iterator for DynamicViewIter {
                 self.next_archetype += 1;
                 let arch = unsafe { self.archetypes.get_unchecked(arch_id).as_ref() };
 
-                if arch.entities().len() == 0 {
+                if arch.entity_indexes().len() == 0 {
                     continue;
                 }
 
@@ -126,7 +126,7 @@ impl Iterator for DynamicViewIter {
                     .map(|q| unsafe { q.fetch(world, ArchetypeId(arch_id as u64), arch) } )
                     .map(|f| FetchDynamicType::from(f))
                     .collect();
-                self.component_indices = 0..arch.entities().len() as u64;
+                self.component_indices = 0..arch.entity_indexes().len() as u64;
             }
         }
     }
@@ -167,7 +167,7 @@ impl ReflectedIterator {
 
             let mut dynamic_row = vec![];
             for d in row.item.iter() {
-                let id = d.info.type_id.as_rust();
+                let id = d.info.type_id().as_rust();
                 let reflected_components = 
                     unsafe { self.reflected_components.as_ref().unwrap().as_ref() };
                 

lyra-scripting/src/lua/world.rs

@@ -192,14 +192,14 @@ impl elua::Userdata for ScriptWorldPtr {
                                         let lua_comp = reflect_user_data(ud);
                                         let refl_comp =
                                             lua_comp.reflect_branch.as_component_unchecked();
-                                        refl_comp.info.type_id.as_rust()
-                                    }
+                                        refl_comp.info.type_id().as_rust()
+                                    },
                                     elua::Value::Table(tbl) => {
                                         let name: String = tbl.get(elua::MetaMethod::Name)?;
 
                                         let lookup = world.get_resource::<LuaTableProxyLookup>();
                                         *lookup.typeid_from_name.get(&name).unwrap()
-                                    }
+                                    },
                                     _ => {
                                         panic!("A userdata or table value was not returned!");
                                         // TODO: Handle properly
@@ -209,8 +209,8 @@ impl elua::Userdata for ScriptWorldPtr {
                                 // update the component tick
                                 let world = unsafe { this.inner.as_mut() };
                                 let arch = world.entity_archetype_mut(row.entity).unwrap();
-                                let idx = arch.entities().get(&row.entity).unwrap().clone();
-                                let c = arch.get_column_mut(lua_typeid.into()).unwrap();
+                                let idx = arch.entity_indexes().get(&row.entity).unwrap().clone();
+                                let c = arch.get_column_mut(lua_typeid).unwrap();
                                 c.entity_ticks[idx.0 as usize] = current;
 
                                 // apply the new component data

lyra-scripting/src/world.rs

@@ -1,6 +1,6 @@
 use std::ptr::NonNull;
 
-use lyra_ecs::{world::World, Entity};
+use lyra_ecs::{World, Entity};
 
 #[derive(Clone)]
 pub struct ScriptEntity(pub Entity);