Trait Resource

pub trait Resource:
    Send
    + Sync
    + 'static { }

A type that can be inserted into a World as a singleton.

You can access resource data in systems using the Res and ResMut system parameters

Only one resource of each type can be stored in a World at any given time.

Examples

#[derive(Resource)]
struct MyResource { value: u32 }

world.insert_resource(MyResource { value: 42 });

fn read_resource_system(resource: Res<MyResource>) {
    assert_eq!(resource.value, 42);
}

fn write_resource_system(mut resource: ResMut<MyResource>) {
    assert_eq!(resource.value, 42);
    resource.value = 0;
    assert_eq!(resource.value, 0);
}

!Sync Resources

A !Sync type cannot implement Resource. However, it is possible to wrap a Send but not Sync type in SyncCell or the currently unstable Exclusive to make it Sync. This forces only having mutable access (&mut T only, never &T), but makes it safe to reference across multiple threads.

This will fail to compile since RefCell is !Sync.

#[derive(Resource)]
struct NotSync {
   counter: RefCell<usize>,
}

This will compile since the RefCell is wrapped with SyncCell.

use bevy_utils::synccell::SyncCell;

#[derive(Resource)]
struct ActuallySync {
   counter: SyncCell<RefCell<usize>>,
}

Implementors

impl Resource for EventRegistry

where Self: Send + Sync + 'static,

impl Resource for AppTypeRegistry

where Self: Send + Sync + 'static,

Available on crate feature bevy_reflect only.

impl Resource for MainThreadExecutor

where Self: Send + Sync + 'static,

impl Resource for Schedules

where Self: Send + Sync + 'static,

impl Resource for Stepping

where Self: Send + Sync + 'static,

impl<E: Event> Resource for Events<E>

where Self: Send + Sync + 'static,

impl<S: System> Resource for CachedSystemId<S>

where Self: Send + Sync + 'static,