Struct ResMut

pub struct ResMut<'w, T: ?Sized + Resource> { /* private fields */ }

Unique mutable borrow of a Resource.

See the Resource documentation for usage.

If you need a shared borrow, use Res instead.

This SystemParam fails validation if resource doesn’t exist. This will cause systems that use this parameter to be skipped.

Use Option<ResMut<T>> instead if the resource might not always exist.

Implementations

impl<'w, T: ?Sized + Resource> ResMut<'w, T>

pub fn into_inner(self) -> &'w mut T

Consume self and return a mutable reference to the contained value while marking self as “changed”.

pub fn reborrow(&mut self) -> Mut<'_, T>

Returns a Mut<> with a smaller lifetime. This is useful if you have &mut ResMut <T>, but you need a Mut<T>.

pub fn map_unchanged<U: ?Sized>( self, f: impl FnOnce(&mut T) -> &mut U, ) -> Mut<'w, U>

Maps to an inner value by applying a function to the contained reference, without flagging a change.

You should never modify the argument passed to the closure – if you want to modify the data without flagging a change, consider using DetectChangesMut::bypass_change_detection to make your intent explicit.

// When run, zeroes the translation of every entity.
fn reset_positions(mut transforms: Query<&mut Transform>) {
    for transform in &mut transforms {
        // We pinky promise not to modify `t` within the closure.
        // Breaking this promise will result in logic errors, but will never cause undefined behavior.
        let mut translation = transform.map_unchanged(|t| &mut t.translation);
        // Only reset the translation if it isn't already zero;
        translation.set_if_neq(Vec2::ZERO);
    }
}

pub fn filter_map_unchanged<U: ?Sized>( self, f: impl FnOnce(&mut T) -> Option<&mut U>, ) -> Option<Mut<'w, U>>

Optionally maps to an inner value by applying a function to the contained reference. This is useful in a situation where you need to convert a Mut<T> to a Mut<U>, but only if T contains U.

As with map_unchanged, you should never modify the argument passed to the closure.

pub fn as_deref_mut(&mut self) -> Mut<'_, <T as Deref>::Target>

where T: DerefMut,

Allows you access to the dereferenced value of this pointer without immediately triggering change detection.

Trait Implementations

impl<'w, T: Resource> AsMut<T> for ResMut<'w, T>

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

Converts this type into a mutable reference of the (usually inferred) input type.

impl<'w, T: Resource> AsRef<T> for ResMut<'w, T>

fn as_ref(&self) -> &T

Converts this type into a shared reference of the (usually inferred) input type.

impl<'w, T> Debug for ResMut<'w, T>

where T: Debug + ?Sized + Resource,

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

Formats the value using the given formatter.

impl<'w, T: ?Sized + Resource> Deref for ResMut<'w, T>

type Target = T

The resulting type after dereferencing.

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

Dereferences the value.

impl<'w, T: ?Sized + Resource> DerefMut for ResMut<'w, T>

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

Mutably dereferences the value.

impl<'w, T: ?Sized + Resource> DetectChanges for ResMut<'w, T>

fn is_added(&self) -> bool

Returns true if this value was added after the system last ran.

fn is_changed(&self) -> bool

Returns true if this value was added or mutably dereferenced either since the last time the system ran or, if the system never ran, since the beginning of the program.

fn last_changed(&self) -> Tick

Returns the change tick recording the time this data was most recently changed.

impl<'w, T: ?Sized + Resource> DetectChangesMut for ResMut<'w, T>

type Inner = T

The type contained within this smart pointer

fn set_changed(&mut self)

Flags this value as having been changed.

fn set_last_changed(&mut self, last_changed: Tick)

Manually sets the change tick recording the time when this data was last mutated.

fn bypass_change_detection(&mut self) -> &mut Self::Inner

Manually bypasses change detection, allowing you to mutate the underlying value without updating the change tick.

fn set_if_neq(&mut self, value: Self::Inner) -> bool

where Self::Inner: Sized + PartialEq,

Overwrites this smart pointer with the given value, if and only if *self != value. Returns true if the value was overwritten, and returns false if it was not.

fn replace_if_neq(&mut self, value: Self::Inner) -> Option<Self::Inner>

where Self::Inner: Sized + PartialEq,

Overwrites this smart pointer with the given value, if and only if *self != value, returning the previous value if this occurs.

impl<'w, T: Resource> From<ResMut<'w, T>> for Mut<'w, T>

fn from(other: ResMut<'w, T>) -> Mut<'w, T>

Convert this ResMut into a Mut. This allows keeping the change-detection feature of Mut while losing the specificity of ResMut for resources.

impl<'w, T: Resource> From<ResMut<'w, T>> for Res<'w, T>

fn from(res: ResMut<'w, T>) -> Self

Converts to this type from the input type.

impl<'w, 'a, T: Resource> IntoIterator for &'a ResMut<'w, T>

where &'a T: IntoIterator,

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

The type of the elements being iterated over.

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

Which kind of iterator are we turning this into?

fn into_iter(self) -> Self::IntoIter

Creates an iterator from a value.

impl<'w, 'a, T: Resource> IntoIterator for &'a mut ResMut<'w, T>

where &'a mut T: IntoIterator,

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

The type of the elements being iterated over.

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

Which kind of iterator are we turning this into?

fn into_iter(self) -> Self::IntoIter

Creates an iterator from a value.

impl<'a, T: Resource> SystemParam for ResMut<'a, T>

type State = ComponentId

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

type Item<'w, 's> = ResMut<'w, T>

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 validate_param( component_id: &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.

unsafe fn get_param<'w, 's>( component_id: &'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 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.