Struct ResMut

pub struct ResMut<'w, T>
where
    T: Resource + ?Sized,
{ /* 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 a panic, but can be configured to do nothing or warn once.

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

Implementations

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

where T: Resource + ?Sized,

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

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

Examples found in repository

examples/stress_tests/bevymark.rs (line 189)

fn scheduled_spawner(
    mut commands: Commands,
    args: Res<Args>,
    window: Single<&Window>,
    mut scheduled: ResMut<BirdScheduled>,
    mut counter: ResMut<BevyCounter>,
    bird_resources: ResMut<BirdResources>,
) {
    if scheduled.waves > 0 {
        let bird_resources = bird_resources.into_inner();
        spawn_birds(
            &mut commands,
            args.into_inner(),
            &window.resolution,
            &mut counter,
            scheduled.per_wave,
            bird_resources,
            None,
            scheduled.waves - 1,
        );

        scheduled.waves -= 1;
    }
}

#[derive(Resource)]
struct BirdResources {
    textures: Vec<Handle<Image>>,
    materials: Vec<Handle<ColorMaterial>>,
    quad: Handle<Mesh>,
    color_rng: ChaCha8Rng,
    material_rng: ChaCha8Rng,
    velocity_rng: ChaCha8Rng,
    transform_rng: ChaCha8Rng,
}

#[derive(Component)]
struct StatsText;

fn setup(
    mut commands: Commands,
    args: Res<Args>,
    asset_server: Res<AssetServer>,
    mut meshes: ResMut<Assets<Mesh>>,
    material_assets: ResMut<Assets<ColorMaterial>>,
    images: ResMut<Assets<Image>>,
    window: Single<&Window>,
    counter: ResMut<BevyCounter>,
) {
    warn!(include_str!("warning_string.txt"));

    let args = args.into_inner();
    let images = images.into_inner();

    let mut textures = Vec::with_capacity(args.material_texture_count.max(1));
    if matches!(args.mode, Mode::Sprite) || args.material_texture_count > 0 {
        textures.push(asset_server.load("branding/icon.png"));
    }
    init_textures(&mut textures, args, images);

    let material_assets = material_assets.into_inner();
    let materials = init_materials(args, &textures, material_assets);

    let mut bird_resources = BirdResources {
        textures,
        materials,
        quad: meshes.add(Rectangle::from_size(Vec2::splat(BIRD_TEXTURE_SIZE as f32))),
        // We're seeding the PRNG here to make this example deterministic for testing purposes.
        // This isn't strictly required in practical use unless you need your app to be deterministic.
        color_rng: ChaCha8Rng::seed_from_u64(42),
        material_rng: ChaCha8Rng::seed_from_u64(42),
        velocity_rng: ChaCha8Rng::seed_from_u64(42),
        transform_rng: ChaCha8Rng::seed_from_u64(42),
    };

    let font = TextFont {
        font_size: 40.0,
        ..Default::default()
    };

    commands.spawn(Camera2d);
    commands
        .spawn((
            Node {
                position_type: PositionType::Absolute,
                padding: UiRect::all(Val::Px(5.0)),
                ..default()
            },
            BackgroundColor(Color::BLACK.with_alpha(0.75)),
            GlobalZIndex(i32::MAX),
        ))
        .with_children(|p| {
            p.spawn((Text::default(), StatsText)).with_children(|p| {
                p.spawn((
                    TextSpan::new("Bird Count: "),
                    font.clone(),
                    TextColor(LIME.into()),
                ));
                p.spawn((TextSpan::new(""), font.clone(), TextColor(AQUA.into())));
                p.spawn((
                    TextSpan::new("\nFPS (raw): "),
                    font.clone(),
                    TextColor(LIME.into()),
                ));
                p.spawn((TextSpan::new(""), font.clone(), TextColor(AQUA.into())));
                p.spawn((
                    TextSpan::new("\nFPS (SMA): "),
                    font.clone(),
                    TextColor(LIME.into()),
                ));
                p.spawn((TextSpan::new(""), font.clone(), TextColor(AQUA.into())));
                p.spawn((
                    TextSpan::new("\nFPS (EMA): "),
                    font.clone(),
                    TextColor(LIME.into()),
                ));
                p.spawn((TextSpan::new(""), font.clone(), TextColor(AQUA.into())));
            });
        });

    let mut scheduled = BirdScheduled {
        per_wave: args.per_wave,
        waves: args.waves,
    };

    if args.benchmark {
        let counter = counter.into_inner();
        for wave in (0..scheduled.waves).rev() {
            spawn_birds(
                &mut commands,
                args,
                &window.resolution,
                counter,
                scheduled.per_wave,
                &mut bird_resources,
                Some(wave),
                wave,
            );
        }
        scheduled.waves = 0;
    }
    commands.insert_resource(bird_resources);
    commands.insert_resource(scheduled);
}

fn mouse_handler(
    mut commands: Commands,
    args: Res<Args>,
    time: Res<Time>,
    mouse_button_input: Res<ButtonInput<MouseButton>>,
    window: Query<&Window>,
    bird_resources: ResMut<BirdResources>,
    mut counter: ResMut<BevyCounter>,
    mut rng: Local<Option<ChaCha8Rng>>,
    mut wave: Local<usize>,
) {
    let Ok(window) = window.single() else {
        return;
    };

    if rng.is_none() {
        // We're seeding the PRNG here to make this example deterministic for testing purposes.
        // This isn't strictly required in practical use unless you need your app to be deterministic.
        *rng = Some(ChaCha8Rng::seed_from_u64(42));
    }
    let rng = rng.as_mut().unwrap();

    if mouse_button_input.just_released(MouseButton::Left) {
        counter.color = Color::linear_rgb(rng.r#gen(), rng.r#gen(), rng.r#gen());
    }

    if mouse_button_input.pressed(MouseButton::Left) {
        let spawn_count = (BIRDS_PER_SECOND as f64 * time.delta_secs_f64()) as usize;
        spawn_birds(
            &mut commands,
            args.into_inner(),
            &window.resolution,
            &mut counter,
            spawn_count,
            bird_resources.into_inner(),
            None,
            *wave,
        );
        *wave += 1;
    }
}

examples/stress_tests/many_materials.rs (line 53)

fn setup(
    mut commands: Commands,
    args: Res<Args>,
    mesh_assets: ResMut<Assets<Mesh>>,
    material_assets: ResMut<Assets<StandardMaterial>>,
) {
    let args = args.into_inner();
    let material_assets = material_assets.into_inner();
    let mesh_assets = mesh_assets.into_inner();
    let n = args.grid_size;

    // Camera
    let w = n as f32;
    commands.spawn((
        Camera3d::default(),
        Transform::from_xyz(w * 1.25, w + 1.0, w * 1.25)
            .looking_at(Vec3::new(0.0, (w * -1.1) + 1.0, 0.0), Vec3::Y),
    ));

    // Light
    commands.spawn((
        Transform::from_rotation(Quat::from_euler(EulerRot::ZYX, 0.0, 1.0, -PI / 4.)),
        DirectionalLight {
            illuminance: 3000.0,
            shadows_enabled: true,
            ..default()
        },
    ));

    // Cubes
    let mesh_handle = mesh_assets.add(Cuboid::from_size(Vec3::ONE));
    for x in 0..n {
        for z in 0..n {
            commands.spawn((
                Mesh3d(mesh_handle.clone()),
                MeshMaterial3d(material_assets.add(Color::WHITE)),
                Transform::from_translation(Vec3::new(x as f32, 0.0, z as f32)),
            ));
        }
    }
}

examples/stress_tests/many_cubes.rs (line 147)

fn setup(
    mut commands: Commands,
    args: Res<Args>,
    mesh_assets: ResMut<Assets<Mesh>>,
    material_assets: ResMut<Assets<StandardMaterial>>,
    images: ResMut<Assets<Image>>,
) {
    warn!(include_str!("warning_string.txt"));

    let args = args.into_inner();
    let images = images.into_inner();
    let material_assets = material_assets.into_inner();
    let mesh_assets = mesh_assets.into_inner();

    let meshes = init_meshes(args, mesh_assets);

    let material_textures = init_textures(args, images);
    let materials = init_materials(args, &material_textures, material_assets);

    // We're seeding the PRNG here to make this example deterministic for testing purposes.
    // This isn't strictly required in practical use unless you need your app to be deterministic.
    let mut material_rng = ChaCha8Rng::seed_from_u64(42);
    match args.layout {
        Layout::Sphere => {
            // NOTE: This pattern is good for testing performance of culling as it provides roughly
            // the same number of visible meshes regardless of the viewing angle.
            const N_POINTS: usize = WIDTH * HEIGHT * 4;
            // NOTE: f64 is used to avoid precision issues that produce visual artifacts in the distribution
            let radius = WIDTH as f64 * 2.5;
            let golden_ratio = 0.5f64 * (1.0f64 + 5.0f64.sqrt());
            for i in 0..N_POINTS {
                let spherical_polar_theta_phi =
                    fibonacci_spiral_on_sphere(golden_ratio, i, N_POINTS);
                let unit_sphere_p = spherical_polar_to_cartesian(spherical_polar_theta_phi);
                let (mesh, transform) = meshes.choose(&mut material_rng).unwrap();
                commands
                    .spawn((
                        Mesh3d(mesh.clone()),
                        MeshMaterial3d(materials.choose(&mut material_rng).unwrap().clone()),
                        Transform::from_translation((radius * unit_sphere_p).as_vec3())
                            .looking_at(Vec3::ZERO, Vec3::Y)
                            .mul_transform(*transform),
                    ))
                    .insert_if(NoFrustumCulling, || args.no_frustum_culling)
                    .insert_if(NoAutomaticBatching, || args.no_automatic_batching);
            }

            // camera
            let mut camera = commands.spawn(Camera3d::default());
            if args.no_indirect_drawing {
                camera.insert(NoIndirectDrawing);
            }
            if args.no_cpu_culling {
                camera.insert(NoCpuCulling);
            }

            // Inside-out box around the meshes onto which shadows are cast (though you cannot see them...)
            commands.spawn((
                Mesh3d(mesh_assets.add(Cuboid::from_size(Vec3::splat(radius as f32 * 2.2)))),
                MeshMaterial3d(material_assets.add(StandardMaterial::from(Color::WHITE))),
                Transform::from_scale(-Vec3::ONE),
                NotShadowCaster,
            ));
        }
        _ => {
            // NOTE: This pattern is good for demonstrating that frustum culling is working correctly
            // as the number of visible meshes rises and falls depending on the viewing angle.
            let scale = 2.5;
            for x in 0..WIDTH {
                for y in 0..HEIGHT {
                    // introduce spaces to break any kind of moiré pattern
                    if x % 10 == 0 || y % 10 == 0 {
                        continue;
                    }
                    // cube
                    commands.spawn((
                        Mesh3d(meshes.choose(&mut material_rng).unwrap().0.clone()),
                        MeshMaterial3d(materials.choose(&mut material_rng).unwrap().clone()),
                        Transform::from_xyz((x as f32) * scale, (y as f32) * scale, 0.0),
                    ));
                    commands.spawn((
                        Mesh3d(meshes.choose(&mut material_rng).unwrap().0.clone()),
                        MeshMaterial3d(materials.choose(&mut material_rng).unwrap().clone()),
                        Transform::from_xyz(
                            (x as f32) * scale,
                            HEIGHT as f32 * scale,
                            (y as f32) * scale,
                        ),
                    ));
                    commands.spawn((
                        Mesh3d(meshes.choose(&mut material_rng).unwrap().0.clone()),
                        MeshMaterial3d(materials.choose(&mut material_rng).unwrap().clone()),
                        Transform::from_xyz((x as f32) * scale, 0.0, (y as f32) * scale),
                    ));
                    commands.spawn((
                        Mesh3d(meshes.choose(&mut material_rng).unwrap().0.clone()),
                        MeshMaterial3d(materials.choose(&mut material_rng).unwrap().clone()),
                        Transform::from_xyz(0.0, (x as f32) * scale, (y as f32) * scale),
                    ));
                }
            }
            // camera
            let center = 0.5 * scale * Vec3::new(WIDTH as f32, HEIGHT as f32, WIDTH as f32);
            commands.spawn((Camera3d::default(), Transform::from_translation(center)));
            // Inside-out box around the meshes onto which shadows are cast (though you cannot see them...)
            commands.spawn((
                Mesh3d(mesh_assets.add(Cuboid::from_size(2.0 * 1.1 * center))),
                MeshMaterial3d(material_assets.add(StandardMaterial::from(Color::WHITE))),
                Transform::from_scale(-Vec3::ONE).with_translation(center),
                NotShadowCaster,
            ));
        }
    }

    commands.spawn((
        DirectionalLight {
            shadows_enabled: args.shadows,
            ..default()
        },
        Transform::IDENTITY.looking_at(Vec3::new(0.0, -1.0, -1.0), Vec3::Y),
    ));
}

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>(self, f: impl FnOnce(&mut T) -> &mut U) -> Mut<'w, U>

where U: ?Sized,

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>( self, f: impl FnOnce(&mut T) -> Option<&mut U>, ) -> Option<Mut<'w, U>>

where U: ?Sized,

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 try_map_unchanged<U, E>( self, f: impl FnOnce(&mut T) -> Result<&mut U, E>, ) -> Result<Mut<'w, U>, E>

where U: ?Sized,

Optionally maps to an inner value by applying a function to the contained reference, returns an error on failure. 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> AsMut<T> for ResMut<'w, T>

where T: Resource,

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

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

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

where T: Resource,

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: Resource + Debug + ?Sized,

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

Formats the value using the given formatter.

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

where T: Resource + ?Sized,

type Target = T

The resulting type after dereferencing.

fn deref(&self) -> &<ResMut<'w, T> as Deref>::Target

Dereferences the value.

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

where T: Resource + ?Sized,

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

Mutably dereferences the value.

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

where T: Resource + ?Sized,

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.

fn added(&self) -> Tick

Returns the change tick recording the time this data was added.

fn changed_by(&self) -> MaybeLocation

The location that last caused this to change.

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

where T: Resource + ?Sized,

type Inner = T

The type contained within this smart pointer

fn set_changed(&mut self)

Flags this value as having been changed.

fn set_added(&mut self)

Flags this value as having been added.

fn set_last_changed(&mut self, last_changed: Tick)

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

fn set_last_added(&mut self, last_added: Tick)

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

fn bypass_change_detection( &mut self, ) -> &mut <ResMut<'w, T> as DetectChangesMut>::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.

fn clone_from_if_neq<T>(&mut self, value: &T) -> bool

where T: ToOwned<Owned = Self::Inner> + ?Sized, Self::Inner: PartialEq<T>,

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

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

where T: Resource,

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> From<ResMut<'w, T>> for Res<'w, T>

where T: Resource,

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

Converts to this type from the input type.

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

where T: Resource, &'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) -> <&'a ResMut<'w, T> as IntoIterator>::IntoIter

Creates an iterator from a value.

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

where T: Resource, &'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) -> <&'a mut ResMut<'w, T> as IntoIterator>::IntoIter

Creates an iterator from a value.

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

where T: Resource,

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, ) -> <ResMut<'a, T> as SystemParam>::State

Registers any World access used by this SystemParam and creates a new instance of this param’s State.

unsafe fn validate_param( _: &<ResMut<'a, T> as SystemParam>::State, _system_meta: &SystemMeta, world: UnsafeWorldCell<'_>, ) -> Result<(), SystemParamValidationError>

Validates that the param can be acquired by the get_param.

unsafe fn get_param<'w, 's>( _: &'s mut <ResMut<'a, T> as SystemParam>::State, system_meta: &SystemMeta, world: UnsafeWorldCell<'w>, change_tick: Tick, ) -> <ResMut<'a, T> as SystemParam>::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 ApplyDeferred.

fn queue( state: &mut Self::State, system_meta: &SystemMeta, world: DeferredWorld<'_>, )

Queues any deferred mutations to be applied at the next ApplyDeferred.