ecs: create a DynamicViewState that can be used to create a dynamic view without dealing with lifetimes

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

@@ -19,16 +19,21 @@ impl DynamicType {
     }
 }
 
-/// A struct that fetches some dynamic type.
+
+/// A struct that fetches a dynamic type.
 /// 
 /// Currently it can only fetch from archetypes, later it will be able to fetch dynamic
 /// resources as well. Its meant to be a single Fetcher for all dynamic types.
-pub struct FetchDynamicType<'a> {
-    pub col: &'a ComponentColumn,
+/// 
+/// # Safety
+/// Internally, this struct has a `NonNull<ComponentColumn>`. You must ensure that the column
+/// is not dropped while this is still alive.
+pub struct FetchDynamicTypeUnsafe {
+    pub col: NonNull<ComponentColumn>,
     pub info: ComponentInfo,
 }
 
-impl<'a> Fetch<'a> for FetchDynamicType<'a> {
+impl<'a> Fetch<'a> for FetchDynamicTypeUnsafe {
     type Item = DynamicType;
 
     fn dangling() -> Self {
@@ -36,7 +41,7 @@ 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 = unsafe { self.col.as_ref() }.borrow_ptr();
         let ptr = NonNull::new_unchecked(ptr.as_ptr()
             .add(entity.0 as usize * self.info.layout().size()));
 
@@ -66,13 +71,13 @@ impl QueryDynamicType {
         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> {
+    pub unsafe fn fetch<'a>(&self, _world: &'a World, _arch_id: crate::archetype::ArchetypeId, archetype: &'a crate::archetype::Archetype) -> FetchDynamicTypeUnsafe {
         let col = archetype.get_column(self.info.type_id())
             .expect("You ignored 'can_visit_archetype'!");
 
-        FetchDynamicType {
-            col,
-            info: self.info,
+        FetchDynamicTypeUnsafe {
+            col: NonNull::from(col),
+            info: self.info
         }
     }
 }

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

@@ -1,18 +1,25 @@
 use std::ops::Range;
 
-use crate::{World, Archetype, ArchetypeEntityId, ArchetypeId, query::Fetch};
+use crate::{query::Fetch, Archetype, ArchetypeEntityId, ArchetypeId, World};
 
-use super::{QueryDynamicType, FetchDynamicType, DynamicType};
+use super::{DynamicType, FetchDynamicTypeUnsafe, QueryDynamicType};
 
-pub struct DynamicView<'a> {
-    world: &'a World,
-    queries: Vec<QueryDynamicType>
+/// Stores the state of a dynamic view.
+/// 
+/// See [`DynamicView`].
+/// 
+/// This backs [`DynamicView`] which you should probably use. The only reason you would use this
+/// instead is if you cant borrow the world when storing this type, and its iterators.
+/// [`DynamicViewState`] provides an 'iterator' of [`DynamicViewStateIter`], which requires you to
+/// provide a world borrow on each `next` of the iterator. View [`DynamicViewStateIter`] for more
+/// info.
+pub struct DynamicViewState {
+    pub(crate) queries: Vec<QueryDynamicType>
 }
 
-impl<'a> DynamicView<'a> {
-    pub fn new(world: &'a World) -> Self {
+impl DynamicViewState {
+    pub fn new() -> Self {
         Self {
-            world,
             queries: Vec::new(),
         }
     }
@@ -20,45 +27,38 @@ impl<'a> DynamicView<'a> {
     pub fn push(&mut self, dyn_query: QueryDynamicType) {
         self.queries.push(dyn_query);
     }
-}
 
-impl<'a> IntoIterator for DynamicView<'a> {
-    type Item = Vec<DynamicType>;
-
-    type IntoIter = DynamicViewIter<'a>;
-
-    fn into_iter(self) -> Self::IntoIter {
-        let archetypes = self.world.archetypes.values().collect();
-
-        DynamicViewIter {
-            world: self.world,
+    pub fn into_iter(self) -> DynamicViewStateIter {
+        DynamicViewStateIter {
             queries: self.queries,
             fetchers: Vec::new(),
-            archetypes,
             next_archetype: 0,
             component_indices: 0..0,
         }
     }
 }
 
-pub struct DynamicViewIter<'a> {
-    pub world: &'a World,
+/// A view iterator on dynamic types.
+/// 
+/// You will likely want to use [`DynamicViewIter`] unless you need to store the iterator
+/// without also borrowing from the world. [`DynamicViewStateIter`] doesn't
+/// actually implement [`Iterator`] since it requires a `&World` to be provided to it
+/// each time `next` is ran (see [`DynamicViewStateIter::next`]).
+pub struct DynamicViewStateIter {
     pub queries: Vec<QueryDynamicType>,
-    pub fetchers: Vec<FetchDynamicType<'a>>,
-    pub archetypes: Vec<&'a Archetype>,
-    pub next_archetype: usize,
-    pub component_indices: Range<u64>,
+    fetchers: Vec<FetchDynamicTypeUnsafe>,
+    next_archetype: usize,
+    component_indices: Range<u64>,
 }
 
-impl<'a> Iterator for DynamicViewIter<'a> {
-    type Item = Vec<DynamicType>;
+impl DynamicViewStateIter {
+    pub fn next(&mut self, world: &World) -> Option<Vec<DynamicType>> {
+        let archetypes = world.archetypes.values().collect::<Vec<_>>();
 
-    fn next(&mut self) -> Option<Self::Item> {
         loop {
             if let Some(entity_index) = self.component_indices.next() {
                 let mut fetch_res = vec![];
 
-                //let fetcher = self.fetcher.as_mut().unwrap();
                 for fetcher in self.fetchers.iter_mut() {
                     let entity_index = ArchetypeEntityId(entity_index);
                     if !fetcher.can_visit_item(entity_index) {
@@ -75,13 +75,13 @@ impl<'a> Iterator for DynamicViewIter<'a> {
                 
                 return Some(fetch_res);
             } else {
-                if self.next_archetype >= self.archetypes.len() {
+                if self.next_archetype >= archetypes.len() {
                     return None; // ran out of archetypes to go through
                 }
 
                 let arch_id = self.next_archetype;
                 self.next_archetype += 1;
-                let arch = unsafe { self.archetypes.get_unchecked(arch_id) };
+                let arch = unsafe { archetypes.get_unchecked(arch_id) };
 
                 if arch.entity_ids.is_empty() {
                     continue;
@@ -92,7 +92,7 @@ impl<'a> Iterator for DynamicViewIter<'a> {
                 }
 
                 self.fetchers = self.queries.iter()
-                    .map(|q| unsafe { q.fetch(self.world, ArchetypeId(arch_id as u64), arch) } )
+                    .map(|q| unsafe { q.fetch(world, ArchetypeId(arch_id as u64), arch) } )
                     .collect();
                 self.component_indices = 0..arch.entity_ids.len() as u64;
             }
@@ -100,13 +100,101 @@ impl<'a> Iterator for DynamicViewIter<'a> {
     }
 }
 
+/// A view of dynamic types (types that are not known to Rust).
+/// 
+/// This view gives you the ability to iterate over types that are unknown to Rust, which we call
+/// dynamic types. This is great for embedding with a scripting language (*cough* *cough* WASM)
+/// since Rust doesn't actually need to know the types of what its iterating over.
+pub struct DynamicView<'a> {
+    world: &'a World,
+    inner: DynamicViewState,
+}
+
+impl<'a> DynamicView<'a> {
+    pub fn new(world: &'a World) -> Self {
+        Self {
+            world,
+            inner: DynamicViewState::new(),
+        }
+    }
+
+    pub fn push(&mut self, dyn_query: QueryDynamicType) {
+        self.inner.queries.push(dyn_query);
+    }
+}
+
+/// A view iterator on dynamic types.
+/// 
+/// This view gives you the ability to iterate over types that are completely unknown to Rust.
+/// This works great for a embedding with a scripting language (*cough* *cough* WASM) since
+/// Rust doesn't actually need to know the types of what its iterating over.
+impl<'a> IntoIterator for DynamicView<'a> {
+    type Item = Vec<DynamicType>;
+
+    type IntoIter = DynamicViewIter<'a>;
+
+    fn into_iter(self) -> Self::IntoIter {
+        let archetypes = self.world.archetypes.values().collect();
+
+        DynamicViewIter {
+            world: self.world,
+            archetypes,
+            inner: self.inner.into_iter(),
+        }
+    }
+}
+
+pub struct DynamicViewIter<'a> {
+    pub world: &'a World,
+    pub archetypes: Vec<&'a Archetype>,
+    inner: DynamicViewStateIter,
+}
+
+impl<'a> Iterator for DynamicViewIter<'a> {
+    type Item = Vec<DynamicType>;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        self.inner.next(&self.world)
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use std::{alloc::Layout, ptr::NonNull};
 
     use crate::{World, ComponentInfo, DynTypeId, DynamicBundle, query::dynamic::QueryDynamicType};
 
-    use super::DynamicView;
+    use super::{DynamicView, DynamicViewState};
+
+    #[test]
+    fn single_dynamic_view_state() {
+        let comp_layout = Layout::new::<u32>();
+        let comp_info = ComponentInfo::new_unknown(Some("u32".to_string()), DynTypeId::Unknown(100), comp_layout);
+
+        let mut dynamic_bundle = DynamicBundle::default();
+        let comp = 50u32;
+        let ptr = NonNull::from(&comp).cast::<u8>();
+        dynamic_bundle.push_unknown(ptr, comp_info.clone());
+
+        let mut world = World::new();
+        world.spawn(dynamic_bundle);
+
+        let query = QueryDynamicType::from_info(comp_info);
+        let mut view = DynamicViewState::new();
+        view.push(query);
+
+        let mut view_iter = view.into_iter();
+        while let Some(view_row) = view_iter.next(&world) {
+            assert_eq!(view_row.len(), 1);
+
+            let mut row_iter = view_row.iter();
+
+            let dynamic_type = row_iter.next().unwrap();
+            
+            let component_data = unsafe { dynamic_type.ptr.cast::<u32>().as_ref() };
+            assert_eq!(*component_data, 50);
+        }
+    }
 
     #[test]
     fn single_dynamic_view() {