Struct bevy::ecs::system::Res

pub struct Res<'w, T>
where T: Resource + ?Sized,
{ /* private fields */ }
Expand description

Shared borrow of a Resource.

See the Resource documentation for usage.

If you need a unique mutable borrow, use ResMut instead.

§Panics

Panics when used as a SystemParameter if the resource does not exist.

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

Implementations§

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impl<'w, T> Res<'w, T>
where T: Resource,

pub fn clone(this: &Res<'w, T>) -> Res<'w, T>

Copies a reference to a resource.

Note that unless you actually need an instance of Res<T>, you should prefer to just convert it to &T which can be freely copied.

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

Due to lifetime limitations of the Deref trait, this method can be used to obtain a reference of the Resource with a lifetime bound to 'w instead of the lifetime of the struct itself.

Examples found in repository?
examples/stress_tests/bevymark.rs (line 167)
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fn scheduled_spawner(
    mut commands: Commands,
    args: Res<Args>,
    windows: Query<&Window>,
    mut scheduled: ResMut<BirdScheduled>,
    mut counter: ResMut<BevyCounter>,
    bird_resources: ResMut<BirdResources>,
) {
    let window = windows.single();

    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: Mesh2dHandle,
    color_rng: ChaCha8Rng,
    material_rng: ChaCha8Rng,
    velocity_rng: ChaCha8Rng,
    transform_rng: ChaCha8Rng,
}

#[derive(Component)]
struct StatsText;

#[allow(clippy::too_many_arguments)]
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>>,
    windows: Query<&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)))
            .into(),
        // 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 text_section = move |color: Srgba, value: &str| {
        TextSection::new(
            value,
            TextStyle {
                font_size: 40.0,
                color: color.into(),
                ..default()
            },
        )
    };

    commands.spawn(Camera2dBundle::default());
    commands
        .spawn(NodeBundle {
            style: Style {
                position_type: PositionType::Absolute,
                padding: UiRect::all(Val::Px(5.0)),
                ..default()
            },
            z_index: ZIndex::Global(i32::MAX),
            background_color: Color::BLACK.with_alpha(0.75).into(),
            ..default()
        })
        .with_children(|c| {
            c.spawn((
                TextBundle::from_sections([
                    text_section(LIME, "Bird Count: "),
                    text_section(AQUA, ""),
                    text_section(LIME, "\nFPS (raw): "),
                    text_section(AQUA, ""),
                    text_section(LIME, "\nFPS (SMA): "),
                    text_section(AQUA, ""),
                    text_section(LIME, "\nFPS (EMA): "),
                    text_section(AQUA, ""),
                ]),
                StatsText,
            ));
        });

    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,
                &windows.single().resolution,
                counter,
                scheduled.per_wave,
                &mut bird_resources,
                Some(wave),
                wave,
            );
        }
        scheduled.waves = 0;
    }
    commands.insert_resource(bird_resources);
    commands.insert_resource(scheduled);
}

#[allow(clippy::too_many_arguments)]
fn mouse_handler(
    mut commands: Commands,
    args: Res<Args>,
    time: Res<Time>,
    mouse_button_input: Res<ButtonInput<MouseButton>>,
    windows: Query<&Window>,
    bird_resources: ResMut<BirdResources>,
    mut counter: ResMut<BevyCounter>,
    mut rng: Local<Option<ChaCha8Rng>>,
    mut wave: Local<usize>,
) {
    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();
    let window = windows.single();

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

    if mouse_button_input.pressed(MouseButton::Left) {
        let spawn_count = (BIRDS_PER_SECOND as f64 * time.delta_seconds_f64()) as usize;
        spawn_birds(
            &mut commands,
            args.into_inner(),
            &window.resolution,
            &mut counter,
            spawn_count,
            bird_resources.into_inner(),
            None,
            *wave,
        );
        *wave += 1;
    }
}
More examples
Hide additional examples
examples/shader/shader_instancing.rs (line 257)
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    fn render<'w>(
        item: &P,
        _view: (),
        instance_buffer: Option<&'w InstanceBuffer>,
        (meshes, render_mesh_instances): SystemParamItem<'w, '_, Self::Param>,
        pass: &mut TrackedRenderPass<'w>,
    ) -> RenderCommandResult {
        let Some(mesh_instance) = render_mesh_instances.render_mesh_queue_data(item.entity())
        else {
            return RenderCommandResult::Failure;
        };
        let Some(gpu_mesh) = meshes.into_inner().get(mesh_instance.mesh_asset_id) else {
            return RenderCommandResult::Failure;
        };
        let Some(instance_buffer) = instance_buffer else {
            return RenderCommandResult::Failure;
        };

        pass.set_vertex_buffer(0, gpu_mesh.vertex_buffer.slice(..));
        pass.set_vertex_buffer(1, instance_buffer.buffer.slice(..));

        match &gpu_mesh.buffer_info {
            GpuBufferInfo::Indexed {
                buffer,
                index_format,
                count,
            } => {
                pass.set_index_buffer(buffer.slice(..), 0, *index_format);
                pass.draw_indexed(0..*count, 0, 0..instance_buffer.length as u32);
            }
            GpuBufferInfo::NonIndexed => {
                pass.draw(0..gpu_mesh.vertex_count, 0..instance_buffer.length as u32);
            }
        }
        RenderCommandResult::Success
    }
examples/stress_tests/many_cubes.rs (line 140)
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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();
                let mut cube = commands.spawn(PbrBundle {
                    mesh: mesh.clone(),
                    material: materials.choose(&mut material_rng).unwrap().clone(),
                    transform: Transform::from_translation((radius * unit_sphere_p).as_vec3())
                        .looking_at(Vec3::ZERO, Vec3::Y)
                        .mul_transform(*transform),
                    ..default()
                });
                if args.no_frustum_culling {
                    cube.insert(NoFrustumCulling);
                }
                if args.no_automatic_batching {
                    cube.insert(NoAutomaticBatching);
                }
            }

            // camera
            let mut camera = commands.spawn(Camera3dBundle::default());
            if args.gpu_culling {
                camera.insert(GpuCulling);
            }
            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((
                PbrBundle {
                    mesh: mesh_assets.add(Cuboid::from_size(Vec3::splat(radius as f32 * 2.2))),
                    material: material_assets.add(StandardMaterial::from(Color::WHITE)),
                    transform: Transform::from_scale(-Vec3::ONE),
                    ..default()
                },
                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(PbrBundle {
                        mesh: meshes.choose(&mut material_rng).unwrap().0.clone(),
                        material: materials.choose(&mut material_rng).unwrap().clone(),
                        transform: Transform::from_xyz((x as f32) * scale, (y as f32) * scale, 0.0),
                        ..default()
                    });
                    commands.spawn(PbrBundle {
                        mesh: meshes.choose(&mut material_rng).unwrap().0.clone(),
                        material: materials.choose(&mut material_rng).unwrap().clone(),
                        transform: Transform::from_xyz(
                            (x as f32) * scale,
                            HEIGHT as f32 * scale,
                            (y as f32) * scale,
                        ),
                        ..default()
                    });
                    commands.spawn(PbrBundle {
                        mesh: meshes.choose(&mut material_rng).unwrap().0.clone(),
                        material: materials.choose(&mut material_rng).unwrap().clone(),
                        transform: Transform::from_xyz((x as f32) * scale, 0.0, (y as f32) * scale),
                        ..default()
                    });
                    commands.spawn(PbrBundle {
                        mesh: meshes.choose(&mut material_rng).unwrap().0.clone(),
                        material: materials.choose(&mut material_rng).unwrap().clone(),
                        transform: Transform::from_xyz(0.0, (x as f32) * scale, (y as f32) * scale),
                        ..default()
                    });
                }
            }
            // camera
            let center = 0.5 * scale * Vec3::new(WIDTH as f32, HEIGHT as f32, WIDTH as f32);
            commands.spawn(Camera3dBundle {
                transform: Transform::from_translation(center),
                ..default()
            });
            // Inside-out box around the meshes onto which shadows are cast (though you cannot see them...)
            commands.spawn((
                PbrBundle {
                    mesh: mesh_assets.add(Cuboid::from_size(2.0 * 1.1 * center)),
                    material: material_assets.add(StandardMaterial::from(Color::WHITE)),
                    transform: Transform::from_scale(-Vec3::ONE).with_translation(center),
                    ..default()
                },
                NotShadowCaster,
            ));
        }
    }

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

Trait Implementations§

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impl<'w, T> AsRef<T> for Res<'w, T>
where T: Resource,

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fn as_ref(&self) -> &T

Converts this type into a shared reference of the (usually inferred) input type.
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impl<'w, T> Debug for Res<'w, T>
where T: Resource + Debug + ?Sized,

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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<'w, T> Deref for Res<'w, T>
where T: Resource + ?Sized,

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type Target = T

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

Dereferences the value.
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impl<'w, T> DetectChanges for Res<'w, T>
where T: Resource + ?Sized,

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fn is_added(&self) -> bool

Returns true if this value was added after the system last ran.
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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. Read more
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fn last_changed(&self) -> Tick

Returns the change tick recording the time this data was most recently changed. Read more
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impl<'w, T> From<ResMut<'w, T>> for Res<'w, T>
where T: Resource,

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

Converts to this type from the input type.
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impl<'w, 'a, T> IntoIterator for &'a Res<'w, T>

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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 Res<'w, T> as IntoIterator>::IntoIter

Creates an iterator from a value. Read more
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impl<'a, T> SystemParam for Res<'a, T>
where T: Resource,

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type State = ComponentId

Used to store data which persists across invocations of a system.
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type Item<'w, 's> = Res<'w, 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 ) -> <Res<'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>( _: &'s mut <Res<'a, T> as SystemParam>::State, system_meta: &SystemMeta, world: UnsafeWorldCell<'w>, change_tick: Tick ) -> <Res<'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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impl<'a, T> ReadOnlySystemParam for Res<'a, T>
where T: Resource,

Auto Trait Implementations§

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impl<'w, T> Freeze for Res<'w, T>
where T: ?Sized,

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impl<'w, T> RefUnwindSafe for Res<'w, T>
where T: RefUnwindSafe + ?Sized,

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impl<'w, T> Send for Res<'w, T>
where T: ?Sized,

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impl<'w, T> Sync for Res<'w, T>
where T: ?Sized,

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impl<'w, T> Unpin for Res<'w, T>
where T: ?Sized,

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impl<'w, T> UnwindSafe for Res<'w, T>
where T: RefUnwindSafe + ?Sized,

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,