DynSystemParam

Struct DynSystemParam 

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pub struct DynSystemParam<'w, 's> { /* private fields */ }
Expand description

A SystemParam with a type that can be configured at runtime.

To be useful, this must be configured using a DynParamBuilder to build the system using a SystemParamBuilder.

§Examples

// If the inner parameter doesn't require any special building, use `ParamBuilder`.
// Either specify the type parameter on `DynParamBuilder::new()` ...
let system = (DynParamBuilder::new::<Res<A>>(ParamBuilder),)
    .build_state(&mut world)
    .build_system(expects_res_a);

// ... or use a factory method on `ParamBuilder` that returns a specific type.
let system = (DynParamBuilder::new(ParamBuilder::resource::<A>()),)
    .build_state(&mut world)
    .build_system(expects_res_a);

fn expects_res_a(mut param: DynSystemParam) {
    // Use the `downcast` methods to retrieve the inner parameter.
    // They will return `None` if the type does not match.
    assert!(param.is::<Res<A>>());
    assert!(!param.is::<Res<B>>());
    assert!(param.downcast_mut::<Res<B>>().is_none());
    let res = param.downcast_mut::<Res<A>>().unwrap();
    // The type parameter can be left out if it can be determined from use.
    let res: Res<A> = param.downcast().unwrap();
}

let system = (
    // If the inner parameter also requires building,
    // pass the appropriate `SystemParamBuilder`.
    DynParamBuilder::new(LocalBuilder(10usize)),
    // `DynSystemParam` is just an ordinary `SystemParam`,
    // and can be combined with other parameters as usual!
    ParamBuilder::query(),
)
    .build_state(&mut world)
    .build_system(|param: DynSystemParam, query: Query<()>| {
        let local: Local<usize> = param.downcast::<Local<usize>>().unwrap();
        assert_eq!(*local, 10);
    });

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impl<'w, 's> DynSystemParam<'w, 's>

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pub fn is<T>(&self) -> bool
where T: SystemParam, <T as SystemParam>::Item<'static, 'static>: SystemParam<Item<'w, 's> = T> + 'static,

Returns true if the inner system param is the same as T.

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pub fn downcast<T>(self) -> Option<T>
where T: SystemParam, <T as SystemParam>::Item<'static, 'static>: SystemParam<Item<'w, 's> = T> + 'static,

Returns the inner system param if it is the correct type. This consumes the dyn param, so the returned param can have its original world and state lifetimes.

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pub fn downcast_mut<'a, T>(&'a mut self) -> Option<T>
where T: SystemParam, <T as SystemParam>::Item<'static, 'static>: SystemParam<Item<'a, 'a> = T> + 'static,

Returns the inner system parameter if it is the correct type. This borrows the dyn param, so the returned param is only valid for the duration of that borrow.

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pub fn downcast_mut_inner<'a, T>(&'a mut self) -> Option<T>
where T: ReadOnlySystemParam, <T as SystemParam>::Item<'static, 'static>: SystemParam<Item<'w, 'a> = T> + 'static,

Returns the inner system parameter if it is the correct type. This borrows the dyn param, so the returned param is only valid for the duration of that borrow, but since it only performs read access it can keep the original world lifetime. This can be useful with methods like Query::iter_inner() or Res::into_inner() to obtain references with the original world lifetime.

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impl SystemParam for DynSystemParam<'_, '_>

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type State = DynSystemParamState

Used to store data which persists across invocations of a system.
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type Item<'world, 'state> = DynSystemParam<'world, 'state>

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, ) -> <DynSystemParam<'_, '_> as SystemParam>::State

Creates a new instance of this param’s State.
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fn init_access( state: &<DynSystemParam<'_, '_> as SystemParam>::State, system_meta: &mut SystemMeta, component_access_set: &mut FilteredAccessSet, world: &mut World, )

Registers any World access used by this SystemParam
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unsafe fn validate_param( state: &mut <DynSystemParam<'_, '_> as SystemParam>::State, system_meta: &SystemMeta, world: UnsafeWorldCell<'_>, ) -> Result<(), SystemParamValidationError>

Validates that the param can be acquired by the get_param. Read more
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unsafe fn get_param<'world, 'state>( state: &'state mut <DynSystemParam<'_, '_> as SystemParam>::State, system_meta: &SystemMeta, world: UnsafeWorldCell<'world>, change_tick: Tick, ) -> <DynSystemParam<'_, '_> as SystemParam>::Item<'world, 'state>

Creates a parameter to be passed into a SystemParamFunction. Read more
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fn apply( state: &mut <DynSystemParam<'_, '_> as SystemParam>::State, system_meta: &SystemMeta, world: &mut World, )

Applies any deferred mutations stored in this SystemParam’s state. This is used to apply Commands during ApplyDeferred.
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fn queue( state: &mut <DynSystemParam<'_, '_> as SystemParam>::State, system_meta: &SystemMeta, world: DeferredWorld<'_>, )

Queues any deferred mutations to be applied at the next ApplyDeferred.
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impl<'a, 'w, 's> SystemParamBuilder<DynSystemParam<'w, 's>> for DynParamBuilder<'a>

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fn build( self, world: &mut World, ) -> <DynSystemParam<'w, 's> 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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fn build_state(self, world: &mut World) -> SystemState<P>

Create a SystemState from a SystemParamBuilder. To create a system, call SystemState::build_system on the result.

Auto Trait Implementations§

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impl<'w, 's> Freeze for DynSystemParam<'w, 's>

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impl<'w, 's> !RefUnwindSafe for DynSystemParam<'w, 's>

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impl<'w, 's> !Send for DynSystemParam<'w, 's>

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impl<'w, 's> !Sync for DynSystemParam<'w, 's>

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impl<'w, 's> Unpin for DynSystemParam<'w, 's>

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impl<'w, 's> !UnwindSafe for DynSystemParam<'w, 's>

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 for T
where T: Any,

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

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

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

Converts &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)

Converts &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> 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> From<T> for T

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fn from(t: T) -> T

Returns the argument unchanged.

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impl<T, W> HasTypeWitness<W> for T
where W: MakeTypeWitness<Arg = T>, T: ?Sized,

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const WITNESS: W = W::MAKE

A constant of the type witness
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impl<T> Identity for T
where T: ?Sized,

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const TYPE_EQ: TypeEq<T, <T as Identity>::Type> = TypeEq::NEW

Proof that Self is the same type as Self::Type, provides methods for casting between Self and Self::Type.
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type Type = T

The same type as Self, used to emulate type equality bounds (T == U) with associated type equality constraints (T: Identity<Type = U>).
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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<T> IntoResult<T> for T

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fn into_result(self) -> Result<T, RunSystemError>

Converts this type into the system output type.
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impl<A> Is for A
where A: Any,

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fn is<T>() -> bool
where T: Any,

Checks if the current type “is” another type, using a TypeId equality comparison. This is most useful in the context of generic logic. Read more
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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> 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