Struct bevy::tasks::Task

pub struct Task<T>(/* private fields */);

Wraps async_executor::Task, a spawned future.

Tasks are also futures themselves and yield the output of the spawned future.

When a task is dropped, its gets canceled and won’t be polled again. To cancel a task a bit more gracefully and wait until it stops running, use the Task::cancel() method.

Tasks that panic get immediately canceled. Awaiting a canceled task also causes a panic.

Implementations

impl<T> Task<T>

pub fn new(task: Task<T>) -> Task<T>

Creates a new task from a given async_executor::Task

pub fn detach(self)

Detaches the task to let it keep running in the background. See async_executor::Task::detach

Examples found in repository

examples/animation/animation_graph.rs (line 197)

fn setup_assets_programmatically(
    commands: &mut Commands,
    asset_server: &mut AssetServer,
    animation_graphs: &mut Assets<AnimationGraph>,
    _save: bool,
) {
    // Create the nodes.
    let mut animation_graph = AnimationGraph::new();
    let blend_node = animation_graph.add_blend(0.5, animation_graph.root);
    animation_graph.add_clip(
        asset_server.load("models/animated/Fox.glb#Animation0"),
        1.0,
        animation_graph.root,
    );
    animation_graph.add_clip(
        asset_server.load("models/animated/Fox.glb#Animation1"),
        1.0,
        blend_node,
    );
    animation_graph.add_clip(
        asset_server.load("models/animated/Fox.glb#Animation2"),
        1.0,
        blend_node,
    );

    // If asked to save, do so.
    #[cfg(not(target_arch = "wasm32"))]
    if _save {
        let animation_graph = animation_graph.clone();

        IoTaskPool::get()
            .spawn(async move {
                let mut animation_graph_writer = File::create(Path::join(
                    &FileAssetReader::get_base_path(),
                    Path::join(Path::new("assets"), Path::new(ANIMATION_GRAPH_PATH)),
                ))
                .expect("Failed to open the animation graph asset");
                ron::ser::to_writer_pretty(
                    &mut animation_graph_writer,
                    &animation_graph,
                    PrettyConfig::default(),
                )
                .expect("Failed to serialize the animation graph");
            })
            .detach();
    }

    // Add the graph.
    let handle = animation_graphs.add(animation_graph);

    // Save the assets in a resource.
    commands.insert_resource(ExampleAnimationGraph(handle));
}

examples/scene/scene.rs (line 145)

fn save_scene_system(world: &mut World) {
    // Scenes can be created from any ECS World.
    // You can either create a new one for the scene or use the current World.
    // For demonstration purposes, we'll create a new one.
    let mut scene_world = World::new();

    // The `TypeRegistry` resource contains information about all registered types (including components).
    // This is used to construct scenes, so we'll want to ensure that our previous type registrations
    // exist in this new scene world as well.
    // To do this, we can simply clone the `AppTypeRegistry` resource.
    let type_registry = world.resource::<AppTypeRegistry>().clone();
    scene_world.insert_resource(type_registry);

    let mut component_b = ComponentB::from_world(world);
    component_b.value = "hello".to_string();
    scene_world.spawn((
        component_b,
        ComponentA { x: 1.0, y: 2.0 },
        Transform::IDENTITY,
        Name::new("joe"),
    ));
    scene_world.spawn(ComponentA { x: 3.0, y: 4.0 });
    scene_world.insert_resource(ResourceA { score: 1 });

    // With our sample world ready to go, we can now create our scene using DynamicScene or DynamicSceneBuilder.
    // For simplicity, we will create our scene using DynamicScene:
    let scene = DynamicScene::from_world(&scene_world);

    // Scenes can be serialized like this:
    let type_registry = world.resource::<AppTypeRegistry>();
    let type_registry = type_registry.read();
    let serialized_scene = scene.serialize(&type_registry).unwrap();

    // Showing the scene in the console
    info!("{}", serialized_scene);

    // Writing the scene to a new file. Using a task to avoid calling the filesystem APIs in a system
    // as they are blocking
    // This can't work in WASM as there is no filesystem access
    #[cfg(not(target_arch = "wasm32"))]
    IoTaskPool::get()
        .spawn(async move {
            // Write the scene RON data to file
            File::create(format!("assets/{NEW_SCENE_FILE_PATH}"))
                .and_then(|mut file| file.write(serialized_scene.as_bytes()))
                .expect("Error while writing scene to file");
        })
        .detach();
}

pub async fn cancel(self) -> Option<T>

Cancels the task and waits for it to stop running.

Returns the task’s output if it was completed just before it got canceled, or None if it didn’t complete.

While it’s possible to simply drop the Task to cancel it, this is a cleaner way of canceling because it also waits for the task to stop running.

See async_executor::Task::cancel

pub fn is_finished(&self) -> bool

Returns true if the current task is finished.

Unlike poll, it doesn’t resolve the final value, it just checks if the task has finished. Note that in a multithreaded environment, this task can be finished immediately after calling this function.

Trait Implementations

impl<T> Debug for Task<T>

where T: Debug,

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl<T> Future for Task<T>

type Output = T

The type of value produced on completion.

fn poll( self: Pin<&mut Task<T>>, cx: &mut Context<'_> ) -> Poll<<Task<T> as Future>::Output>

Attempt to resolve the future to a final value, registering the current task for wakeup if the value is not yet available.