Struct bevy::prelude::Local

pub struct Local<'s, T>(/* private fields */)
where
    T: FromWorld + Send + 'static;
Expand description

A system local SystemParam.

A local may only be accessed by the system itself and is therefore not visible to other systems. If two or more systems specify the same local type each will have their own unique local. If multiple SystemParams within the same system each specify the same local type each will get their own distinct data storage.

The supplied lifetime parameter is the SystemParams 's lifetime.

§Examples

fn write_to_local(mut local: Local<usize>) {
    *local = 42;
}
fn read_from_local(local: Local<usize>) -> usize {
    *local
}
let mut write_system = IntoSystem::into_system(write_to_local);
let mut read_system = IntoSystem::into_system(read_from_local);
write_system.initialize(world);
read_system.initialize(world);

assert_eq!(read_system.run((), world), 0);
write_system.run((), world);
// Note how the read local is still 0 due to the locals not being shared.
assert_eq!(read_system.run((), world), 0);

N.B. A Locals value cannot be read or written to outside of the containing system. To add configuration to a system, convert a capturing closure into the system instead:

struct Config(u32);
#[derive(Resource)]
struct MyU32Wrapper(u32);
fn reset_to_system(value: Config) -> impl FnMut(ResMut<MyU32Wrapper>) {
    move |mut val| val.0 = value.0
}

// .add_systems(reset_to_system(my_config))

Trait Implementations§

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impl<'w, T> BuildableSystemParam for Local<'w, T>
where T: FromWorld + Send + 'static,

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type Builder<'b> = T

A mutable reference to this type will be passed to the builder function
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fn build( world: &mut World, _meta: &mut SystemMeta, func: impl FnOnce(&mut <Local<'w, T> as BuildableSystemParam>::Builder<'_>), ) -> <Local<'w, T> as SystemParam>::State

Constructs SystemParam::State for Self using a given builder function
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impl<'s, T> Debug for Local<'s, T>
where T: Debug + FromWorld + Send + 'static,

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fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter. Read more
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impl<'s, T> Deref for Local<'s, T>
where T: FromWorld + Send + 'static,

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type Target = T

The resulting type after dereferencing.
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fn deref(&self) -> &<Local<'s, T> as Deref>::Target

Dereferences the value.
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impl<'s, T> DerefMut for Local<'s, T>
where T: FromWorld + Send + 'static,

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fn deref_mut(&mut self) -> &mut <Local<'s, T> as Deref>::Target

Mutably dereferences the value.
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impl<'_s, T> ExclusiveSystemParam for Local<'_s, T>
where T: FromWorld + Send + 'static,

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type State = SyncCell<T>

Used to store data which persists across invocations of a system.
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type Item<'s> = Local<'s, T>

The item type returned when constructing this system param. See SystemParam::Item.
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fn init( world: &mut World, _system_meta: &mut SystemMeta, ) -> <Local<'_s, T> as ExclusiveSystemParam>::State

Creates a new instance of this param’s State.
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fn get_param<'s>( state: &'s mut <Local<'_s, T> as ExclusiveSystemParam>::State, _system_meta: &SystemMeta, ) -> <Local<'_s, T> as ExclusiveSystemParam>::Item<'s>

Creates a parameter to be passed into an ExclusiveSystemParamFunction.
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impl<'s, 'a, T> IntoIterator for &'a Local<'s, T>
where T: FromWorld + Send + 'static, &'a T: IntoIterator,

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type Item = <&'a T as IntoIterator>::Item

The type of the elements being iterated over.
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type IntoIter = <&'a T as IntoIterator>::IntoIter

Which kind of iterator are we turning this into?
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fn into_iter(self) -> <&'a Local<'s, T> as IntoIterator>::IntoIter

Creates an iterator from a value. Read more
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impl<'s, 'a, T> IntoIterator for &'a mut Local<'s, T>
where T: FromWorld + Send + 'static, &'a mut T: IntoIterator,

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type Item = <&'a mut T as IntoIterator>::Item

The type of the elements being iterated over.
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type IntoIter = <&'a mut T as IntoIterator>::IntoIter

Which kind of iterator are we turning this into?
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fn into_iter(self) -> <&'a mut Local<'s, T> as IntoIterator>::IntoIter

Creates an iterator from a value. Read more
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impl<'a, T> SystemParam for Local<'a, T>
where T: FromWorld + Send + 'static,

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type State = SyncCell<T>

Used to store data which persists across invocations of a system.
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type Item<'w, 's> = Local<'s, T>

The item type returned when constructing this system param. The value of this associated type should be Self, instantiated with new lifetimes. Read more
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fn init_state( world: &mut World, _system_meta: &mut SystemMeta, ) -> <Local<'a, T> as SystemParam>::State

Registers any World access used by this SystemParam and creates a new instance of this param’s State.
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unsafe fn get_param<'w, 's>( state: &'s mut <Local<'a, T> as SystemParam>::State, _system_meta: &SystemMeta, _world: UnsafeWorldCell<'w>, _change_tick: Tick, ) -> <Local<'a, T> as SystemParam>::Item<'w, 's>

Creates a parameter to be passed into a SystemParamFunction. Read more
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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 Read more
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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.
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fn queue( state: &mut Self::State, system_meta: &SystemMeta, world: DeferredWorld<'_>, )

Queues any deferred mutations to be applied at the next apply_deferred.
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impl<'s, T> ReadOnlySystemParam for Local<'s, T>
where T: FromWorld + Send + 'static,

Auto Trait Implementations§

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impl<'s, T> Freeze for Local<'s, T>

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impl<'s, T> RefUnwindSafe for Local<'s, T>
where T: RefUnwindSafe,

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impl<'s, T> Send for Local<'s, T>

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impl<'s, T> Sync for Local<'s, T>
where T: Sync,

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impl<'s, T> Unpin for Local<'s, T>

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impl<'s, T> !UnwindSafe for Local<'s, T>

Blanket Implementations§

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impl<T> Any for T
where T: 'static + ?Sized,

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fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
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impl<T, U> AsBindGroupShaderType<U> for T
where U: ShaderType, &'a T: for<'a> Into<U>,

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fn as_bind_group_shader_type(&self, _images: &RenderAssets<GpuImage>) -> U

Return the T ShaderType for self. When used in AsBindGroup derives, it is safe to assume that all images in self exist.
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impl<T> Borrow<T> for T
where T: ?Sized,

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fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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impl<T> BorrowMut<T> for T
where T: ?Sized,

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fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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impl<T> Downcast<T> for T

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fn downcast(&self) -> &T

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impl<T> Downcast for T
where T: Any,

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fn into_any(self: Box<T>) -> Box<dyn Any>

Convert Box<dyn Trait> (where Trait: Downcast) to Box<dyn Any>. Box<dyn Any> can then be further downcast into Box<ConcreteType> where ConcreteType implements Trait.
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fn into_any_rc(self: Rc<T>) -> Rc<dyn Any>

Convert Rc<Trait> (where Trait: Downcast) to Rc<Any>. Rc<Any> can then be further downcast into Rc<ConcreteType> where ConcreteType implements Trait.
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fn as_any(&self) -> &(dyn Any + 'static)

Convert &Trait (where Trait: Downcast) to &Any. This is needed since Rust cannot generate &Any’s vtable from &Trait’s.
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fn as_any_mut(&mut self) -> &mut (dyn Any + 'static)

Convert &mut Trait (where Trait: Downcast) to &Any. This is needed since Rust cannot generate &mut Any’s vtable from &mut Trait’s.
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impl<T> DowncastSync for T
where T: Any + Send + Sync,

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fn into_any_arc(self: Arc<T>) -> Arc<dyn Any + Sync + Send>

Convert Arc<Trait> (where Trait: Downcast) to Arc<Any>. Arc<Any> can then be further downcast into Arc<ConcreteType> where ConcreteType implements Trait.
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impl<T> From<T> for T

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fn from(t: T) -> T

Returns the argument unchanged.

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impl<S> FromSample<S> for S

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fn from_sample_(s: S) -> S

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impl<T> Instrument for T

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fn instrument(self, span: Span) -> Instrumented<Self>

Instruments this type with the provided Span, returning an Instrumented wrapper. Read more
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fn in_current_span(self) -> Instrumented<Self>

Instruments this type with the current Span, returning an Instrumented wrapper. Read more
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impl<T, U> Into<U> for T
where U: From<T>,

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fn into(self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

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impl<T> IntoEither for T

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fn into_either(self, into_left: bool) -> Either<Self, Self>

Converts self into a Left variant of Either<Self, Self> if into_left is true. Converts self into a Right variant of Either<Self, Self> otherwise. Read more
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fn into_either_with<F>(self, into_left: F) -> Either<Self, Self>
where F: FnOnce(&Self) -> bool,

Converts self into a Left variant of Either<Self, Self> if into_left(&self) returns true. Converts self into a Right variant of Either<Self, Self> otherwise. Read more
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impl<F, T> IntoSample<T> for F
where T: FromSample<F>,

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fn into_sample(self) -> T

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impl<T> Pointable for T

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const ALIGN: usize = _

The alignment of pointer.
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type Init = T

The type for initializers.
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unsafe fn init(init: <T as Pointable>::Init) -> usize

Initializes a with the given initializer. Read more
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unsafe fn deref<'a>(ptr: usize) -> &'a T

Dereferences the given pointer. Read more
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unsafe fn deref_mut<'a>(ptr: usize) -> &'a mut T

Mutably dereferences the given pointer. Read more
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unsafe fn drop(ptr: usize)

Drops the object pointed to by the given pointer. Read more
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impl<T> Same for T

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type Output = T

Should always be Self
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impl<T, U> ToSample<U> for T
where U: FromSample<T>,

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fn to_sample_(self) -> U

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impl<T, U> TryFrom<U> for T
where U: Into<T>,

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type Error = Infallible

The type returned in the event of a conversion error.
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fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

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type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.
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impl<T> Upcast<T> for T

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fn upcast(&self) -> Option<&T>

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impl<V, T> VZip<V> for T
where V: MultiLane<T>,

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fn vzip(self) -> V

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impl<T> WithSubscriber for T

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fn with_subscriber<S>(self, subscriber: S) -> WithDispatch<Self>
where S: Into<Dispatch>,

Attaches the provided Subscriber to this type, returning a WithDispatch wrapper. Read more
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fn with_current_subscriber(self) -> WithDispatch<Self>

Attaches the current default Subscriber to this type, returning a WithDispatch wrapper. Read more
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impl<T> ConditionalSend for T
where T: Send,

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impl<S, T> Duplex<S> for T
where T: FromSample<S> + ToSample<S>,

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impl<T> Settings for T
where T: 'static + Send + Sync,

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impl<T> WasmNotSend for T
where T: Send,

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impl<T> WasmNotSendSync for T
where T: WasmNotSend + WasmNotSync,

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impl<T> WasmNotSync for T
where T: Sync,