create SimpleSystem

src/ecs/mod.rs

@@ -1 +1,57 @@
+use std::collections::HashMap;
+
+use async_trait::async_trait;
+use hecs::World;
+use tracing::warn;
+
 pub mod components;
+
+/// A trait that represents a simple system
+pub trait SimpleSystem {
+    // todo: make async?
+    fn execute_mut(&mut self, world: &mut World) -> anyhow::Result<()>;
+}
+
+pub type SystemFn = dyn Fn(&mut World) -> anyhow::Result<()>;
+
+pub struct SystemFnExecutor {
+    systems: HashMap<String, Box<SystemFn>>,
+}
+
+impl SystemFnExecutor {
+    pub fn new() -> Self {
+        Self {
+            systems: HashMap::new(),
+        }
+    }
+
+    pub fn with_systems(systems: HashMap<String, Box<SystemFn>>) -> Self {
+        Self {
+            systems,
+        }
+    }
+
+    pub fn add_system(&mut self, system_label: &str, system: Box<SystemFn>) {
+        self.systems.insert(system_label.to_string(), system);
+    }
+
+    pub fn remove_system(&mut self, system_label: &str) {
+        self.systems.remove(&system_label.to_string());
+    }
+}
+
+impl SimpleSystem for SystemFnExecutor {
+    fn execute_mut(&mut self, world: &mut World) -> anyhow::Result<()> {
+        for system in self.systems.iter() {
+            let system_fn = system.1.as_ref();
+            let res = system_fn(world);
+
+            // log an error returned by the system
+            if let Err(e) = res {
+                warn!("System execution of {} resulted in an error! '{}'", system.0, e);
+            }
+        }
+
+        Ok(())
+    }
+}

src/game.rs

@@ -75,6 +75,7 @@ struct GameLoop {
     renderer: Box<dyn Renderer>,
     
     world: Arc<Mutex<World>>,
+    system_fn_executor: SystemFnExecutor,
     fps_counter: TickCounter,
 }
 
@@ -85,6 +86,7 @@ impl GameLoop {
             renderer: Box::new(BasicRenderer::create_with_window(window).await),
 
             world,
+            system_fn_executor: SystemFnExecutor::new(),
             fps_counter: TickCounter::new(),
         }
     }
@@ -98,10 +100,8 @@ impl GameLoop {
     }
 
     async fn update(&mut self) {
-        /* let world = self.world.lock().await;
-        for dispatcher in self.system_dispatchers.iter_mut() {
-            dispatcher.dispatch(&world);
-        } */
+        let mut world = self.world.lock().await;
+        self.system_fn_executor.execute_mut(&mut world).unwrap(); // always returns Ok(())
     }
 
     async fn input_update(&mut self, event: &InputEvent) -> Option<ControlFlow> {