Struct Single

pub struct Single<'w, D: QueryData, F: QueryFilter = ()> { /* private fields */ }

System parameter that provides access to single entity’s components, much like Query::single/Query::single_mut.

This SystemParam fails validation if zero or more than one matching entity exists. /// This will cause a panic, but can be configured to do nothing or warn once.

Use Option<Single<D, F>> instead if zero or one matching entities can exist.

See Query for more details.

Implementations

impl<'w, D: QueryData, F: QueryFilter> Single<'w, D, F>

pub fn into_inner(self) -> D::Item<'w>

Returns the inner item with ownership.

Trait Implementations

impl<'w, D: QueryData, F: QueryFilter> Deref for Single<'w, D, F>

type Target = <D as WorldQuery>::Item<'w>

The resulting type after dereferencing.

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

Dereferences the value.

impl<'w, D: QueryData, F: QueryFilter> DerefMut for Single<'w, D, F>

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

Mutably dereferences the value.

impl<'a, D: QueryData + 'static, F: QueryFilter + 'static> SystemParam for Single<'a, D, F>

type State = QueryState<D, F>

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

type Item<'w, 's> = Single<'w, D, F>

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

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 validate_param( state: &Self::State, system_meta: &SystemMeta, world: UnsafeWorldCell<'_>, ) -> 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.

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<'a, D: ReadOnlyQueryData + 'static, F: QueryFilter + 'static> ReadOnlySystemParam for Single<'a, D, F>