Trait Event 

pub trait Event:
    Sized
    + Send
    + Sync
    + 'static {
    type Trigger<'a>: Trigger<Self>;
}

An Event is something that “happens” at a given moment.

To make an Event “happen”, you “trigger” it on a World using World::trigger or via a Command using Commands::trigger. This causes any Observer watching for that Event to run immediately, as part of the World::trigger call.

First, we create an Event type, typically by deriving the trait.

#[derive(Event)]
struct Speak {
    message: String,
}

Then, we add an Observer to watch for this event type:

world.add_observer(|speak: On<Speak>| {
    println!("{}", speak.message);
});

Finally, we trigger the event by calling World::trigger:

world.trigger(Speak {
    message: "Hello!".to_string(),
});

Triggers

Every Event has an associated Trigger implementation (set via Event::Trigger), which defines which observers will run, what data will be passed to them, and the order they will be run in. Unless you are an internals developer or you have very specific needs, you don’t need to worry too much about Trigger. When you derive Event (or a more specific event trait like EntityEvent), a Trigger will be provided for you.

The Event derive defaults Event::Trigger to GlobalTrigger, which will run all observers that watch for the Event.

Entity Events

For events that “target” a specific Entity, see EntityEvent.

Required Associated Types

type Trigger<'a>: Trigger<Self>

Defines which observers will run, what data will be passed to them, and the order they will be run in. See Trigger for more info.

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Implementations on Foreign Types

impl Event for AcquireFocus

where AcquireFocus: Send + Sync + 'static,

type Trigger<'a> = PropagateEntityTrigger<true, AcquireFocus, WindowTraversal>

impl<M> Event for FocusedInput<M>

where M: Message + Clone, FocusedInput<M>: Send + Sync + 'static,

type Trigger<'a> = PropagateEntityTrigger<true, FocusedInput<M>, WindowTraversal>

Implementors

impl Event for CheckChangeTicks

where CheckChangeTicks: Send + Sync + 'static,

type Trigger<'a> = GlobalTrigger

impl Event for ReadbackComplete

where ReadbackComplete: Send + Sync + 'static,

type Trigger<'a> = EntityTrigger

impl Event for ScreenshotCaptured

where ScreenshotCaptured: Send + Sync + 'static,

type Trigger<'a> = EntityTrigger

impl Event for Add

where Add: Send + Sync + 'static,

type Trigger<'a> = EntityComponentsTrigger<'a>

impl Event for Despawn

where Despawn: Send + Sync + 'static,

type Trigger<'a> = EntityComponentsTrigger<'a>

impl Event for Insert

where Insert: Send + Sync + 'static,

type Trigger<'a> = EntityComponentsTrigger<'a>

impl Event for Remove

where Remove: Send + Sync + 'static,

type Trigger<'a> = EntityComponentsTrigger<'a>

impl Event for Replace

where Replace: Send + Sync + 'static,

type Trigger<'a> = EntityComponentsTrigger<'a>

impl<E> Event for Pointer<E>

where E: Debug + Clone + Reflect, Pointer<E>: Send + Sync + 'static,

type Trigger<'a> = PropagateEntityTrigger<true, Pointer<E>, PointerTraversal>