Struct bevy::ecs::system::RemovedComponents

pub struct RemovedComponents<'a, T>where
    T: Component,{ /* private fields */ }

A SystemParam that grants access to the entities that had their T Component removed.

Note that this does not allow you to see which data existed before removal. If you need this, you will need to track the component data value on your own, using a regularly scheduled system that requests Query<(Entity, &T), Changed<T>> and stores the data somewhere safe to later cross-reference.

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 itself, this is automatically done in a system added by MinimalPlugins or DefaultPlugins at the end of each pass of the game loop during the CoreStage::Last stage. As such RemovedComponents systems should be scheduled after the stage where removal occurs but before CoreStage::Last.

Examples

Basic usage:

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

Implementations

impl<'a, T> RemovedComponents<'a, T>where
    T: Component,

pub fn iter(&self) -> Cloned<Iter<'_, Entity>>

Returns an iterator over the entities that had their T Component removed.

Trait Implementations

impl<'a, T> IntoIterator for &'a RemovedComponents<'a, T>where
    T: Component,

type Item = Entity

The type of the elements being iterated over.

type IntoIter = Cloned<Iter<'a, Entity>>

Which kind of iterator are we turning this into?

fn into_iter(self) -> <&'a RemovedComponents<'a, T> as IntoIterator>::IntoIter

Creates an iterator from a value.

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

type Fetch = RemovedComponentsState<T>