Add dynamic schedule example

Author: Alainx277

Cargo.toml

@@ -317,6 +317,10 @@ path = "examples/ecs/timers.rs"
 name = "query_bundle"
 path = "examples/ecs/query_bundle.rs"
 
+[[example]]
+name = "dynamic_schedule"
+path = "examples/ecs/dynamic_schedule.rs"
+
 # Games
 [[example]]
 name = "alien_cake_addict"

examples/README.md

@@ -170,6 +170,7 @@ Example | File | Description
 `system_param` | [`ecs/system_param.rs`](./ecs/system_param.rs) | Illustrates creating custom system parameters with `SystemParam`
 `system_sets` | [`ecs/system_sets.rs`](./ecs/system_sets.rs) | Shows `SystemSet` use along with run criterion
 `timers` | [`ecs/timers.rs`](./ecs/timers.rs) | Illustrates ticking `Timer` resources inside systems and handling their state
+`dynamic_schedule` | [`ecs/dynamic_schedule.rs`](./ecs/dynamic_schedule.rs) | Shows how to modify the schedule from systems
 
 ## Games
 

examples/ecs/dynamic_schedule.rs

@@ -0,0 +1,38 @@
+use bevy::{core::FixedTimestep, prelude::*};
+use rand::Rng;
+
+fn main() {
+    App::build()
+        .add_plugins(DefaultPlugins)
+        .add_stage_after(
+            CoreStage::Update,
+            "slow",
+            SystemStage::parallel().with_run_criteria(FixedTimestep::step(1.0)),
+        )
+        .add_startup_system(setup)
+        .add_system(dynamic.with_run_criteria(FixedTimestep::step(1.0)))
+        .run();
+}
+
+fn setup(mut commands: Commands) {
+    commands.spawn_bundle(OrthographicCameraBundle::new_2d());
+}
+
+fn dynamic(mut commands: Commands, mut system_counter: Local<u64>) {
+    let count = system_counter.clone();
+    *system_counter += 1;
+    let closure = move |mut commands: Commands,
+                        asset_server: Res<AssetServer>,
+                        mut materials: ResMut<Assets<ColorMaterial>>| {
+        info!("Hello from system {}", count);
+
+        let mut rng = rand::thread_rng();
+        let texture_handle = asset_server.load("branding/icon.png");
+        commands.spawn_bundle(SpriteBundle {
+            material: materials.add(texture_handle.into()),
+            transform: Transform::from_xyz(rng.gen_range(-400f32..400f32), rng.gen_range(-400f32..400f32), 0.0),
+            ..Default::default()
+        });
+    };
+    commands.insert_system(closure, "slow");
+}