Struct Extract

pub struct Extract<'w, 's, P>
where
    P: ReadOnlySystemParam + 'static,
{ /* private fields */ }

A helper for accessing MainWorld content using a system parameter.

A SystemParam adapter which applies the contained SystemParam to the World contained in MainWorld. This parameter only works for systems run during the ExtractSchedule.

This requires that the contained SystemParam does not mutate the world, as it uses a read-only reference to MainWorld internally.

Context

ExtractSchedule is used to extract (move) data from the simulation world (MainWorld) to the render world. The render world drives rendering each frame (generally to a Window). This design is used to allow performing calculations related to rendering a prior frame at the same time as the next frame is simulated, which increases throughput (FPS).

Extract is used to get data from the main world during ExtractSchedule.

Examples

use bevy_ecs::prelude::*;
use bevy_render::Extract;
fn extract_clouds(mut commands: Commands, clouds: Extract<Query<Entity, With<Cloud>>>) {
    for cloud in &clouds {
        commands.get_or_spawn(cloud).insert(Cloud);
    }
}

Trait Implementations

impl<'w, 's, P> Deref for Extract<'w, 's, P>

where P: ReadOnlySystemParam,

type Target = <P as SystemParam>::Item<'w, 's>

The resulting type after dereferencing.

fn deref(&self) -> &Self::Target

Dereferences the value.

impl<'w, 's, P> DerefMut for Extract<'w, 's, P>

where P: ReadOnlySystemParam,

fn deref_mut(&mut self) -> &mut Self::Target

Mutably dereferences the value.

impl<'a, 'w, 's, P> IntoIterator for &'a Extract<'w, 's, P>

where P: ReadOnlySystemParam, &'a SystemParamItem<'w, 's, P>: IntoIterator,

type Item = <&'a <P as SystemParam>::Item<'w, 's> as IntoIterator>::Item

The type of the elements being iterated over.

type IntoIter = <&'a <P as SystemParam>::Item<'w, 's> as IntoIterator>::IntoIter

Which kind of iterator are we turning this into?

fn into_iter(self) -> Self::IntoIter

Creates an iterator from a value.

impl<P> SystemParam for Extract<'_, '_, P>

where P: ReadOnlySystemParam,

type State = ExtractState<P>

Used to store data which persists across invocations of a system.

type Item<'w, 's> = Extract<'w, 's, P>

The item type returned when constructing this system param. The value of this associated type should be Self, instantiated with new lifetimes.

fn init_state(world: &mut World, system_meta: &mut SystemMeta) -> Self::State

Registers any World access used by this SystemParam and creates a new instance of this param’s State.

unsafe fn get_param<'w, 's>( state: &'s mut Self::State, system_meta: &SystemMeta, world: UnsafeWorldCell<'w>, change_tick: Tick, ) -> Self::Item<'w, 's>

Creates a parameter to be passed into a SystemParamFunction.

unsafe fn new_archetype( state: &mut Self::State, archetype: &Archetype, system_meta: &mut SystemMeta, )

For the specified Archetype, registers the components accessed by this SystemParam (if applicable).a

fn apply(state: &mut Self::State, system_meta: &SystemMeta, world: &mut World)

Applies any deferred mutations stored in this SystemParam’s state. This is used to apply Commands during apply_deferred.

fn queue( state: &mut Self::State, system_meta: &SystemMeta, world: DeferredWorld<'_>, )

Queues any deferred mutations to be applied at the next apply_deferred.

impl<P> ReadOnlySystemParam for Extract<'_, '_, P>

where P: ReadOnlySystemParam,