RemovedComponents

Struct RemovedComponents 

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pub struct RemovedComponents<'w, 's, T>
where T: Component,
{ /* private fields */ }
Expand description

A SystemParam that yields entities that had their T Component removed or have been despawned with it.

This acts effectively the same as a MessageReader.

Unlike hooks or observers (see the lifecycle module docs), this does not allow you to see which data existed before removal.

If you are using bevy_ecs as a standalone crate, note that the RemovedComponents list will not be automatically cleared for you, and will need to be manually flushed using World::clear_trackers.

For users of bevy and bevy_app, World::clear_trackers is automatically called by bevy_app::App::update and bevy_app::SubApp::update. For the main world, this is delayed until after all SubApps have run.

§Examples

Basic usage:

fn react_on_removal(mut removed: RemovedComponents<MyComponent>) {
    removed.read().for_each(|removed_entity| println!("{}", removed_entity));
}

Implementations§

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impl<'w, 's, T> RemovedComponents<'w, 's, T>
where T: Component,

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pub fn reader(&self) -> &MessageCursor<RemovedComponentEntity>

Fetch underlying MessageCursor.

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pub fn reader_mut(&mut self) -> &mut MessageCursor<RemovedComponentEntity>

Fetch underlying MessageCursor mutably.

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pub fn events(&self) -> Option<&Messages<RemovedComponentEntity>>

👎Deprecated since 0.17.0: Renamed to messages.

Fetch underlying Messages.

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pub fn messages(&self) -> Option<&Messages<RemovedComponentEntity>>

Fetch underlying Messages.

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pub fn reader_mut_with_messages( &mut self, ) -> Option<(&mut RemovedComponentReader<T>, &Messages<RemovedComponentEntity>)>

Destructures to get a mutable reference to the MessageCursor and a reference to Messages.

This is necessary since Rust can’t detect destructuring through methods and most usecases of the reader uses the Messages as well.

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pub fn reader_mut_with_events( &mut self, ) -> Option<(&mut RemovedComponentReader<T>, &Messages<RemovedComponentEntity>)>

👎Deprecated since 0.17.0: Renamed to reader_mut_with_messages.

Destructures to get a reference to the MessageCursor and a reference to Messages.

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pub fn read( &mut self, ) -> Map<Flatten<IntoIter<Cloned<MessageIterator<'_, RemovedComponentEntity>>>>, fn(RemovedComponentEntity) -> Entity>

Iterates over the messages this RemovedComponents has not seen yet. This updates the RemovedComponents’s message counter, which means subsequent message reads will not include messages that happened before now.

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pub fn read_with_id( &mut self, ) -> Map<Flatten<IntoIter<MessageIteratorWithId<'_, RemovedComponentEntity>>>, fn((&RemovedComponentEntity, MessageId<RemovedComponentEntity>)) -> (Entity, MessageId<RemovedComponentEntity>)>

Like read, except also returning the MessageId of the messages.

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pub fn len(&self) -> usize

Determines the number of removal messages available to be read from this RemovedComponents without consuming any.

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pub fn is_empty(&self) -> bool

Returns true if there are no messages available to read.

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pub fn clear(&mut self)

Consumes all available messages.

This means these messages will not appear in calls to RemovedComponents::read() or RemovedComponents::read_with_id() and RemovedComponents::is_empty() will return true.

Trait Implementations§

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impl<T> SystemParam for RemovedComponents<'_, '_, T>
where T: Component,

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type State = FetchState<T>

Used to store data which persists across invocations of a system.
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type Item<'w, 's> = RemovedComponents<'w, 's, T>

The item type returned when constructing this system param. The value of this associated type should be Self, instantiated with new lifetimes. Read more
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fn init_state( world: &mut World, ) -> <RemovedComponents<'_, '_, T> as SystemParam>::State

Creates a new instance of this param’s State.
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fn init_access( state: &<RemovedComponents<'_, '_, T> as SystemParam>::State, system_meta: &mut SystemMeta, component_access_set: &mut FilteredAccessSet, world: &mut World, )

Registers any World access used by this SystemParam
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fn apply( state: &mut <RemovedComponents<'_, '_, T> as SystemParam>::State, system_meta: &SystemMeta, world: &mut World, )

Applies any deferred mutations stored in this SystemParam’s state. This is used to apply Commands during ApplyDeferred.
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fn queue( state: &mut <RemovedComponents<'_, '_, T> as SystemParam>::State, system_meta: &SystemMeta, world: DeferredWorld<'_>, )

Queues any deferred mutations to be applied at the next ApplyDeferred.
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unsafe fn validate_param<'w, 's>( state: &'s mut <RemovedComponents<'_, '_, T> as SystemParam>::State, _system_meta: &SystemMeta, _world: UnsafeWorldCell<'w>, ) -> Result<(), SystemParamValidationError>

Validates that the param can be acquired by the get_param. Read more
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unsafe fn get_param<'w, 's>( state: &'s mut <RemovedComponents<'_, '_, T> as SystemParam>::State, system_meta: &SystemMeta, world: UnsafeWorldCell<'w>, change_tick: Tick, ) -> <RemovedComponents<'_, '_, T> as SystemParam>::Item<'w, 's>

Creates a parameter to be passed into a SystemParamFunction. Read more
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impl<'w, 's, T> ReadOnlySystemParam for RemovedComponents<'w, 's, T>

Auto Trait Implementations§

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impl<'w, 's, T> Freeze for RemovedComponents<'w, 's, T>

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impl<'w, 's, T> RefUnwindSafe for RemovedComponents<'w, 's, T>
where T: RefUnwindSafe,

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impl<'w, 's, T> Send for RemovedComponents<'w, 's, T>

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impl<'w, 's, T> Sync for RemovedComponents<'w, 's, T>

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impl<'w, 's, T> Unpin for RemovedComponents<'w, 's, T>

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impl<'w, 's, T> !UnwindSafe for RemovedComponents<'w, 's, T>

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where T: 'static + ?Sized,

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