Struct ParallelCommands

pub struct ParallelCommands<'w, 's> { /* private fields */ }

An alternative to Commands that can be used in parallel contexts, such as those in Query::par_iter.

For cases where multiple non-computation-heavy (lightweight) bundles of the same Bundle type need to be spawned, consider using Commands::spawn_batch for better performance.

Note: Because command application order will depend on how many threads are ran, non-commutative commands may result in non-deterministic results.

Example:

fn parallel_command_system(
    mut query: Query<(Entity, &Velocity)>,
    par_commands: ParallelCommands
) {
    query.par_iter().for_each(|(entity, velocity)| {
        if velocity.magnitude() > 10.0 {
            par_commands.command_scope(|mut commands| {
                commands.entity(entity).despawn();
            });
        }
    });
}

Implementations

impl<'w, 's> ParallelCommands<'w, 's>

pub fn command_scope<R>(&self, f: impl FnOnce(Commands<'_, '_>) -> R) -> R

Temporarily provides access to the Commands for the current thread.

For an example, see the type-level documentation for ParallelCommands.

Trait Implementations

impl SystemParam for ParallelCommands<'_, '_>

type State = FetchState

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

type Item<'w, 's> = ParallelCommands<'w, 's>

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 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.

unsafe fn validate_param<'w, 's>( state: &'s Self::State, system_meta: &SystemMeta, world: UnsafeWorldCell<'w>, ) -> bool

Validates that the param can be acquired by the get_param. Built-in executors use this to prevent systems with invalid params from running. For nested SystemParams validation will fail if any delegated validation fails.

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.

impl<'w, 's> ReadOnlySystemParam for ParallelCommands<'w, 's>

where Deferred<'s, ParallelCommandQueue>: ReadOnlySystemParam, &'w Entities: ReadOnlySystemParam,