Struct bevy_app::SubApp

pub struct SubApp {
    pub app: App,
    /* private fields */
}

A SubApp contains its own Schedule and World separate from the main App. This is useful for situations where data and data processing should be kept completely separate from the main application. The primary use of this feature in bevy is to enable pipelined rendering.

Example

#[derive(Resource, Default)]
struct Val(pub i32);

#[derive(Debug, Clone, Copy, Hash, PartialEq, Eq, AppLabel)]
struct ExampleApp;

let mut app = App::new();

// initialize the main app with a value of 0;
app.insert_resource(Val(10));

// create a app with a resource and a single schedule
let mut sub_app = App::empty();
// add an outer schedule that runs the main schedule
sub_app.insert_resource(Val(100));

// initialize main schedule
sub_app.add_systems(Main, |counter: Res<Val>| {
    // since we assigned the value from the main world in extract
    // we see that value instead of 100
    assert_eq!(counter.0, 10);
});

// add the sub_app to the app
app.insert_sub_app(ExampleApp, SubApp::new(sub_app, |main_world, sub_app| {
    // extract the value from the main app to the sub app
    sub_app.world.resource_mut::<Val>().0 = main_world.resource::<Val>().0;
}));

// This will run the schedules once, since we're using the default runner
app.run();

Fields

app: App

The SubApp’s instance of App

Implementations

impl SubApp

pub fn new( app: App, extract: impl Fn(&mut World, &mut App) + Send + 'static ) -> Self

Creates a new SubApp.

The provided function extract is normally called by the update method. After extract is called, the Schedule of the sub app is run. The World parameter represents the main app world, while the App parameter is just a mutable reference to the SubApp itself.

pub fn run(&mut self)

Runs the SubApp’s default schedule.

pub fn extract(&mut self, main_world: &mut World)

Extracts data from main world to this sub-app.

Trait Implementations

impl Debug for SubApp

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

Formats the value using the given formatter.