impl Default for EventReader

crates/bevy_app/src/event/event.rs

@@ -1,4 +1,4 @@
-use legion::prelude::{ResMut, Resources};
+use legion::prelude::ResMut;
 use std::marker::PhantomData;
 
 #[derive(Debug)]
@@ -87,6 +87,15 @@ pub struct EventReader<T> {
     _marker: PhantomData<T>,
 }
 
+impl<T> Default for EventReader<T> {
+    fn default() -> Self {
+        Self {
+            last_event_count: 0,
+            _marker: PhantomData::default(),
+        }
+    }
+}
+
 impl<T> EventReader<T> {
     /// Iterates over the events this EventReader has not seen yet. This updates the EventReader's
     /// event counter, which means subsequent event reads will not include events that happened before now.
@@ -245,25 +254,6 @@ impl<T> Events<T> {
     }
 }
 
-pub trait GetEventReader {
-    /// returns an [EventReader] of the given type
-    fn get_event_reader<T>(&self) -> EventReader<T>
-    where
-        T: Send + Sync + 'static;
-}
-
-impl GetEventReader for Resources {
-    fn get_event_reader<T>(&self) -> EventReader<T>
-    where
-        T: Send + Sync + 'static,
-    {
-        let my_event = self
-            .get::<Events<T>>()
-            .unwrap_or_else(|| panic!("Event does not exist: {}", std::any::type_name::<T>()));
-        my_event.get_reader()
-    }
-}
-
 #[cfg(test)]
 mod tests {
     use super::*;

crates/bevy_app/src/resources.rs

@@ -1,4 +1,3 @@
-use crate::{EventReader, GetEventReader};
 use legion::prelude::Resources;
 
 pub trait FromResources {
@@ -12,13 +11,4 @@ where
     default fn from_resources(_resources: &Resources) -> Self {
         Self::default()
     }
-}
-
-impl<T> FromResources for EventReader<T>
-where
-    T: Send + Sync + 'static,
-{
-    fn from_resources(resources: &Resources) -> Self {
-        resources.get_event_reader::<T>()
-    }
-}
+}

crates/bevy_app/src/schedule_runner.rs

@@ -1,5 +1,5 @@
-use super::{App, AppBuilder, AppPlugin, GetEventReader};
-use crate::{AppExit, Events};
+use super::{App, AppBuilder, AppPlugin};
+use crate::{AppExit, Events, EventReader};
 use std::{thread, time::Duration};
 
 #[derive(Copy, Clone, Debug)]
@@ -39,7 +39,7 @@ impl AppPlugin for ScheduleRunnerPlugin {
     fn build(&self, app: &mut AppBuilder) {
         let run_mode = self.run_mode;
         app.set_runner(move |mut app: App| {
-            let mut app_exit_event_reader = app.resources.get_event_reader::<AppExit>();
+            let mut app_exit_event_reader = EventReader::<AppExit>::default();
             match run_mode {
                 RunMode::Once => {
                     if let Some(ref mut schedule) = app.schedule {

crates/bevy_input/src/system.rs

@@ -1,9 +1,9 @@
 use crate::keyboard::{ElementState, KeyboardInput, VirtualKeyCode};
-use bevy_app::{AppExit, Events, GetEventReader};
+use bevy_app::{AppExit, EventReader, Events};
 use legion::prelude::*;
 
-pub fn exit_on_esc_system(resources: &mut Resources) -> Box<dyn Schedulable> {
-    let mut keyboard_input_event_reader = resources.get_event_reader::<KeyboardInput>();
+pub fn exit_on_esc_system(_resources: &mut Resources) -> Box<dyn Schedulable> {
+    let mut keyboard_input_event_reader = EventReader::<KeyboardInput>::default();
     (move |keyboard_input_events: Res<Events<KeyboardInput>>,
            mut app_exit_events: ResMut<Events<AppExit>>| {
         for event in keyboard_input_event_reader.iter(&keyboard_input_events) {

crates/bevy_render/src/base_render_graph/mod.rs

@@ -7,15 +7,10 @@ use crate::{
         nodes::{CameraNode, PassNode, TextureCopyNode, WindowSwapChainNode, WindowTextureNode},
         RenderGraph,
     },
-    texture::{
-        Extent3d, Texture, TextureDescriptor, TextureDimension, TextureFormat, TextureUsage,
-    },
+    texture::{Extent3d, TextureDescriptor, TextureDimension, TextureFormat, TextureUsage},
     Color,
 };
-use bevy_app::GetEventReader;
-use bevy_asset::AssetEvent;
-use bevy_window::{WindowCreated, WindowReference, WindowResized};
-use legion::prelude::Resources;
+use bevy_window::WindowReference;
 
 pub struct BaseRenderGraphConfig {
     pub add_2d_camera: bool,
@@ -58,7 +53,6 @@ impl Default for BaseRenderGraphConfig {
 pub trait BaseRenderGraphBuilder {
     fn add_base_graph(
         &mut self,
-        resources: &Resources,
         config: &BaseRenderGraphConfig,
     ) -> &mut Self;
 }
@@ -66,13 +60,9 @@ pub trait BaseRenderGraphBuilder {
 impl BaseRenderGraphBuilder for RenderGraph {
     fn add_base_graph(
         &mut self,
-        resources: &Resources,
         config: &BaseRenderGraphConfig,
     ) -> &mut Self {
-        self.add_node(
-            node::TEXTURE_COPY,
-            TextureCopyNode::new(resources.get_event_reader::<AssetEvent<Texture>>()),
-        );
+        self.add_node(node::TEXTURE_COPY, TextureCopyNode::default());
         if config.add_3d_camera {
             self.add_system_node(node::CAMERA, CameraNode::new(uniform::CAMERA));
         }
@@ -98,8 +88,6 @@ impl BaseRenderGraphBuilder for RenderGraph {
                         format: TextureFormat::Depth32Float, // PERF: vulkan docs recommend using 24 bit depth for better performance
                         usage: TextureUsage::OUTPUT_ATTACHMENT,
                     },
-                    resources.get_event_reader::<WindowCreated>(),
-                    resources.get_event_reader::<WindowResized>(),
                 ),
             );
         }
@@ -141,11 +129,7 @@ impl BaseRenderGraphBuilder for RenderGraph {
 
         self.add_node(
             node::PRIMARY_SWAP_CHAIN,
-            WindowSwapChainNode::new(
-                WindowReference::Primary,
-                resources.get_event_reader::<WindowCreated>(),
-                resources.get_event_reader::<WindowResized>(),
-            ),
+            WindowSwapChainNode::new(WindowReference::Primary),
         );
 
         if config.connect_main_pass_to_swapchain {

crates/bevy_render/src/camera/camera.rs

@@ -1,5 +1,5 @@
 use crate::CameraProjection;
-use bevy_app::{Events, GetEventReader};
+use bevy_app::{EventReader, Events};
 use bevy_property::Properties;
 use bevy_window::WindowResized;
 use glam::Mat4;
@@ -12,9 +12,9 @@ pub struct Camera {
 }
 
 pub fn camera_system<T: CameraProjection + Component>(
-    resources: &mut Resources,
+    _resources: &mut Resources,
 ) -> Box<dyn Schedulable> {
-    let mut window_resized_event_reader = resources.get_event_reader::<WindowResized>();
+    let mut window_resized_event_reader = EventReader::<WindowResized>::default();
     (move |world: &mut SubWorld,
            window_resized_events: Res<Events<WindowResized>>,
            query: &mut Query<(Write<Camera>, Write<T>)>| {

crates/bevy_render/src/lib.rs

@@ -113,7 +113,7 @@ impl AppPlugin for RenderPlugin {
         if let Some(ref config) = self.base_render_graph_config {
             let resources = app.resources();
             let mut render_graph = resources.get_mut::<RenderGraph>().unwrap();
-            render_graph.add_base_graph(resources, config);
+            render_graph.add_base_graph(config);
         }
     }
 }

crates/bevy_render/src/mesh.rs

@@ -8,7 +8,7 @@ use crate::{
     shader::AsUniforms,
     Renderable, Vertex,
 };
-use bevy_app::{Events, GetEventReader};
+use bevy_app::{EventReader, Events};
 use bevy_asset::{AssetEvent, Assets, Handle};
 use bevy_core::bytes::AsBytes;
 use glam::*;
@@ -337,7 +337,7 @@ fn remove_current_mesh_resources(
 
 pub fn mesh_resource_provider_system(resources: &mut Resources) -> Box<dyn Schedulable> {
     let mut vertex_buffer_descriptors = resources.get_mut::<VertexBufferDescriptors>().unwrap();
-    let mut mesh_event_reader = resources.get_event_reader::<AssetEvent<Mesh>>();
+    let mut mesh_event_reader = EventReader::<AssetEvent<Mesh>>::default();
     // TODO: allow pipelines to specialize on vertex_buffer_descriptor and index_format
     let vertex_buffer_descriptor = Vertex::get_vertex_buffer_descriptor().unwrap();
     vertex_buffer_descriptors.set(vertex_buffer_descriptor.clone());

crates/bevy_render/src/render_graph/nodes/texture_copy_node.rs

@@ -9,18 +9,11 @@ use bevy_asset::{AssetEvent, Assets};
 
 use legion::prelude::*;
 
+#[derive(Default)]
 pub struct TextureCopyNode {
     pub texture_event_reader: EventReader<AssetEvent<Texture>>,
 }
 
-impl TextureCopyNode {
-    pub fn new(texture_event_reader: EventReader<AssetEvent<Texture>>) -> Self {
-        TextureCopyNode {
-            texture_event_reader,
-        }
-    }
-}
-
 impl Node for TextureCopyNode {
     fn update(
         &mut self,

crates/bevy_render/src/render_graph/nodes/window_swapchain_node.rs

@@ -18,13 +18,11 @@ impl WindowSwapChainNode {
     pub const OUT_TEXTURE: &'static str = "texture";
     pub fn new(
         window_reference: WindowReference,
-        window_created_event_reader: EventReader<WindowCreated>,
-        window_resized_event_reader: EventReader<WindowResized>,
     ) -> Self {
         WindowSwapChainNode {
             window_reference,
-            window_created_event_reader,
-            window_resized_event_reader,
+            window_created_event_reader: Default::default(),
+            window_resized_event_reader: Default::default(),
         }
     }
 }

crates/bevy_render/src/render_graph/nodes/window_texture_node.rs

@@ -21,14 +21,12 @@ impl WindowTextureNode {
     pub fn new(
         window_reference: WindowReference,
         descriptor: TextureDescriptor,
-        window_created_event_reader: EventReader<WindowCreated>,
-        window_resized_event_reader: EventReader<WindowResized>,
     ) -> Self {
         WindowTextureNode {
             window_reference,
             descriptor,
-            window_created_event_reader,
-            window_resized_event_reader,
+            window_created_event_reader: Default::default(),
+            window_resized_event_reader: Default::default(),
         }
     }
 }

crates/bevy_render/src/texture/texture.rs

@@ -5,7 +5,6 @@ use crate::{
 };
 use bevy_app::{EventReader, Events};
 use bevy_asset::{AssetEvent, Assets, Handle};
-use bevy_derive::FromResources;
 use glam::Vec2;
 use legion::prelude::*;
 use std::{collections::HashSet, fs::File};
@@ -108,7 +107,7 @@ impl Texture {
     }
 }
 
-#[derive(FromResources)]
+#[derive(Default)]
 pub struct TextureResourceSystemState {
     event_reader: EventReader<AssetEvent<Texture>>,
 }

crates/bevy_scene/src/scene_spawner.rs

@@ -1,5 +1,5 @@
 use crate::Scene;
-use bevy_app::{EventReader, Events, FromResources, GetEventReader};
+use bevy_app::{EventReader, Events};
 use bevy_asset::{AssetEvent, Assets, Handle};
 use bevy_type_registry::TypeRegistry;
 use legion::{
@@ -26,6 +26,8 @@ impl InstanceId {
         InstanceId(Uuid::new_v4())
     }
 }
+
+#[derive(Default)]
 pub struct SceneSpawner {
     loaded_scenes: HashSet<Handle<Scene>>,
     spawned_scenes: HashMap<Handle<Scene>, Vec<InstanceId>>,
@@ -35,19 +37,6 @@ pub struct SceneSpawner {
     scenes_to_load: Vec<Handle<Scene>>,
 }
 
-impl FromResources for SceneSpawner {
-    fn from_resources(resources: &Resources) -> Self {
-        SceneSpawner {
-            scene_asset_event_reader: resources.get_event_reader::<AssetEvent<Scene>>(),
-            spawned_scenes: Default::default(),
-            spawned_instances: Default::default(),
-            loaded_scenes: Default::default(),
-            scenes_to_spawn: Default::default(),
-            scenes_to_load: Default::default(),
-        }
-    }
-}
-
 #[derive(Error, Debug)]
 pub enum SceneSpawnError {
     #[error("Scene contains an unregistered component.")]

crates/bevy_window/src/lib.rs

@@ -43,7 +43,7 @@ impl AppPlugin for WindowPlugin {
         }
 
         if self.exit_on_close {
-            let exit_on_close_system = exit_on_window_close_system(app.resources_mut(), None);
+            let exit_on_close_system = exit_on_window_close_system(None);
             app.add_system(exit_on_close_system);
         }
     }

crates/bevy_window/src/system.rs

@@ -1,13 +1,9 @@
 use crate::{WindowCloseRequested, WindowId};
-use bevy_app::{AppExit, Events, GetEventReader};
+use bevy_app::{AppExit, EventReader, Events};
 use legion::prelude::*;
 
-pub fn exit_on_window_close_system(
-    resources: &mut Resources,
-    window_id: Option<WindowId>,
-) -> Box<dyn Schedulable> {
-    let mut window_close_requested_event_reader =
-        resources.get_event_reader::<WindowCloseRequested>();
+pub fn exit_on_window_close_system(window_id: Option<WindowId>) -> Box<dyn Schedulable> {
+    let mut window_close_requested_event_reader = EventReader::<WindowCloseRequested>::default();
     SystemBuilder::new("exit_on_window_close")
         .read_resource::<Events<WindowCloseRequested>>()
         .write_resource::<Events<AppExit>>()

crates/bevy_winit/src/lib.rs

@@ -7,7 +7,7 @@ use bevy_input::{
     mouse::{MouseButtonInput, MouseMotionInput},
 };
 
-use bevy_app::{App, AppBuilder, AppExit, AppPlugin, EventReader, Events, GetEventReader};
+use bevy_app::{App, AppBuilder, AppExit, AppPlugin, EventReader, Events};
 use bevy_window::{
     CreateWindow, CursorMoved, Window, WindowCloseRequested, WindowCreated, WindowResized, Windows,
 };
@@ -35,8 +35,8 @@ impl AppPlugin for WinitPlugin {
 
 pub fn winit_runner(mut app: App) {
     let event_loop = EventLoop::new();
-    let mut create_window_event_reader = app.resources.get_event_reader::<CreateWindow>();
-    let mut app_exit_event_reader = app.resources.get_event_reader::<AppExit>();
+    let mut create_window_event_reader = EventReader::<CreateWindow>::default();
+    let mut app_exit_event_reader = EventReader::<AppExit>::default();
 
     handle_create_window_events(
         &mut app.resources,

examples/ecs/event.rs

@@ -43,7 +43,7 @@ fn event_trigger_system(
     }
 }
 
-#[derive(FromResources)]
+#[derive(Default)]
 struct EventListenerState {
     my_event_reader: EventReader<MyEvent>,
 }

examples/input/input_keyboard.rs

@@ -13,7 +13,7 @@ fn main() {
         .run();
 }
 
-#[derive(FromResources)]
+#[derive(Default)]
 struct State {
     event_reader: EventReader<KeyboardInput>,
     moving_right: bool,

examples/input/input_mouse.rs

@@ -12,7 +12,7 @@ fn main() {
         .run();
 }
 
-#[derive(FromResources)]
+#[derive(Default)]
 struct State {
     mouse_button_event_reader: EventReader<MouseButtonInput>,
     mouse_motion_event_reader: EventReader<MouseMotionInput>,

examples/scene/load_scene.rs

@@ -35,14 +35,14 @@ struct ComponentA {
 struct ComponentB {
     pub value: String,
     #[property(ignore)]
-    pub event_reader: EventReader<KeyboardInput>,
+    pub time_since_startup: std::time::Duration,
 }
 
 impl FromResources for ComponentB {
     fn from_resources(resources: &Resources) -> Self {
-        let event_reader = resources.get_event_reader::<KeyboardInput>();
+        let time = resources.get::<Time>().unwrap();
         ComponentB {
-            event_reader,
+            time_since_startup: time.time_since_startup(),
             value: "Default Value".to_string(),
         }
     }

src/prelude.rs

@@ -50,7 +50,7 @@ pub use crate::window::{Window, WindowDescriptor, WindowPlugin, Windows};
 pub use crate::{
     app::{
         schedule_runner::ScheduleRunnerPlugin, stage, App, AppBuilder, AppPlugin, EntityArchetype,
-        EventReader, Events, FromResources, GetEventReader, System,
+        EventReader, Events, FromResources, System,
     },
     math::{self, Mat3, Mat4, Quat, Vec2, Vec3, Vec4},
     AddDefaultPlugins,