Struct bevy_render::Extract

pub struct Extract<'w, 's, P: SystemParam + 'static> where
    P::Fetch: ReadOnlySystemParamFetch, { /* 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 RenderStage::Extract.

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

Context

RenderStage::Extract 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 RenderStage::Extract.

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.iter() {
        commands.get_or_spawn(cloud).insert(Cloud);
    }
}

Trait Implementations

impl<'w, 's, P: SystemParam> Deref for Extract<'w, 's, P> where
    P::Fetch: ReadOnlySystemParamFetch, 

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

The resulting type after dereferencing.

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

Dereferences the value.

impl<'w, 's, P: SystemParam> DerefMut for Extract<'w, 's, P> where
    P::Fetch: ReadOnlySystemParamFetch, 

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

Mutably dereferences the value.

impl<'w, 's, P: SystemParam> SystemParam for Extract<'w, 's, P> where
    P::Fetch: ReadOnlySystemParamFetch, 

type Fetch = ExtractState<P>