Resource system functions

crates/bevy_app/src/app_builder.rs

@@ -207,6 +207,16 @@ impl AppBuilder {
         self
     }
 
+    pub fn add_resource_init<R>(&mut self) -> &mut Self
+    where
+        R: for<'a> From<&'a mut Resources> + Send + Sync + 'static,
+    {
+        let resources = self.resources_mut();
+        let resource = R::from(resources);
+        resources.insert(resource);
+        self
+    }
+
     pub fn set_runner(&mut self, run_fn: impl Fn(App) + 'static) -> &mut Self {
         self.app_mut().runner = Some(Box::new(run_fn));
         self

crates/bevy_legion/legion_systems/src/lib.rs

@@ -16,6 +16,6 @@ pub mod prelude {
         resource::{ResourceSet, Resources, PreparedRead as Resource, PreparedWrite as ResourceMut},
         schedule::{Executor, Runnable, Schedulable, Schedule},
         System, SystemBuilder,
-        into_system,
+        into_system, into_resource_system
     };
 }

crates/bevy_legion/legion_systems/src/system_fn.rs

@@ -14,11 +14,11 @@ use std::marker::PhantomData;
 use bit_set::BitSet;
 
 
-pub fn into_system<'a, Q, F, R, X>(name: &'static str, system: F) -> Box<dyn Schedulable>
+pub fn into_system<'a, Q, F, R, X>(name: &'static str, mut system: F) -> Box<dyn Schedulable>
 where
     Q: IntoQuery + DefaultFilter<Filter = R>,
     <Q as View<'a>>::Iter: Iterator<Item = Q> + 'a,
-    F: Fn(&mut X, Q) + Send + Sync + 'static,
+    F: FnMut(&mut X, Q) + Send + Sync + 'static,
     R: EntityFilter + Sync + 'static,
     X: ResourceSet<PreparedResources = X> + 'static,
 {
@@ -57,6 +57,41 @@ where
     })
 }
 
+pub fn into_resource_system<'a, F, X>(name: &'static str, mut system: F) -> Box<dyn Schedulable>
+where
+    F: FnMut(&mut X) + Send + Sync + 'static,
+    X: ResourceSet<PreparedResources = X> + 'static,
+{
+    let mut resource_access: Access<ResourceTypeId> = Access::default();
+    resource_access.reads.extend(X::read_types().iter());
+    resource_access.writes.extend(X::write_types().iter());
+
+    let component_access: Access<ComponentTypeId> = Access::default();
+    let run_fn = SystemFnWrapper(
+        move |_,
+              _,
+              resources: &mut X,
+              _| {
+            system(resources);
+        },
+        PhantomData,
+    );
+
+    Box::new(System {
+        name: name.into(),
+        queries: AtomicRefCell::new(()),
+        access: SystemAccess {
+            resources: resource_access,
+            components: component_access,
+            tags: Access::default(),
+        },
+        archetypes: ArchetypeAccess::Some(BitSet::default()),
+        _resources: PhantomData::<X>,
+        command_buffer: FxHashMap::default(),
+        run_fn: AtomicRefCell::new(run_fn),
+    })
+}
+
 #[cfg(test)]
 mod tests {
     use super::into_system;

examples/event.rs

@@ -1,44 +1,63 @@
 use bevy::prelude::*;
 
-struct MyEvent {
-    pub message: String,
-}
-
 fn main() {
     App::build()
         .add_default_plugins()
         .add_event::<MyEvent>()
-        .add_system(event_trigger_system())
-        .add_system_init(event_listener_system)
+        .add_resource(EventTriggerState::default())
+        .add_resource_init::<EventListenerState>()
+        .add_system(into_resource_system("event_trigger", event_trigger_system))
+        .add_system(into_resource_system(
+            "event_listener",
+            event_listener_system,
+        ))
         .run();
 }
 
-// sends MyEvent every second
-fn event_trigger_system() -> Box<dyn Schedulable> {
-    let mut elapsed = 0.0;
-    SystemBuilder::new("event_trigger")
-        .read_resource::<Time>()
-        .write_resource::<Events<MyEvent>>()
-        .build(move |_, _, (time, my_events), _| {
-            elapsed += time.delta_seconds;
-            if elapsed > 1.0 {
-                my_events.send(MyEvent {
-                    message: "Hello World".to_string(),
-                });
+struct MyEvent {
+    pub message: String,
+}
 
-                elapsed = 0.0;
-            }
-        })
+#[derive(Default)]
+struct EventTriggerState {
+    elapsed: f32,
+}
+
+// sends MyEvent every second
+fn event_trigger_system(
+    (state, my_events, time): &mut (
+        ResourceMut<EventTriggerState>,
+        ResourceMut<Events<MyEvent>>,
+        Resource<Time>,
+    ),
+) {
+    state.elapsed += time.delta_seconds;
+    if state.elapsed > 1.0 {
+        my_events.send(MyEvent {
+            message: "Hello World".to_string(),
+        });
+
+        state.elapsed = 0.0;
+    }
+}
+
+struct EventListenerState {
+    my_event_reader: EventReader<MyEvent>,
+}
+
+impl From<&mut Resources> for EventListenerState {
+    fn from(resources: &mut Resources) -> Self {
+        EventListenerState {
+            my_event_reader: resources.get_event_reader::<MyEvent>(),
+        }
+    }
 }
 
 // prints events as they come in
-fn event_listener_system(resources: &mut Resources) -> Box<dyn Schedulable> {
-    let mut my_event_reader = resources.get_event_reader::<MyEvent>();
-    SystemBuilder::new("event_listener")
-        .read_resource::<Events<MyEvent>>()
-        .build(move |_, _, my_events, _| {
-            for my_event in my_events.iter(&mut my_event_reader) {
-                println!("{}", my_event.message);
-            }
-        })
-}
+fn event_listener_system(
+    (state, my_events): &mut (ResourceMut<EventListenerState>, Resource<Events<MyEvent>>),
+) {
+    for my_event in my_events.iter(&mut state.my_event_reader) {
+        println!("{}", my_event.message);
+    }
+}

src/prelude.rs

@@ -55,7 +55,7 @@ pub use legion::{
         resource::{ResourceSet, Resources, PreparedRead as Resource, PreparedWrite as ResourceMut},
         schedule::{Executor, Runnable, Schedulable, Schedule},
         SubWorld, System, SystemBuilder,
-        into_system
+        into_system, into_resource_system
     },
     world::{Universe, World},
 };