Struct bevy::ecs::schedule::NextState

pub struct NextState<S>(pub Option<S>)
where
    S: States;

The next state of State<S>.

To queue a transition, just set the contained value to Some(next_state). Note that these transitions can be overridden by other systems: only the actual value of this resource at the time of apply_state_transition matters.

use bevy_ecs::prelude::*;

#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug, Default, States)]
enum GameState {
    #[default]
    MainMenu,
    SettingsMenu,
    InGame,
}

fn start_game(mut next_game_state: ResMut<NextState<GameState>>) {
    next_game_state.set(GameState::InGame);
}

Tuple Fields

0: Option<S>

Implementations

impl<S> NextState<S>

where S: States,

pub fn set(&mut self, state: S)

Tentatively set a planned state transition to Some(state).

Examples found in repository

examples/ecs/generic_system.rs (line 79)

fn transition_to_in_game_system(
    mut next_state: ResMut<NextState<AppState>>,
    keyboard_input: Res<ButtonInput<KeyCode>>,
) {
    if keyboard_input.pressed(KeyCode::Space) {
        next_state.set(AppState::InGame);
    }
}

examples/games/game_menu.rs (line 112)

    fn countdown(
        mut game_state: ResMut<NextState<GameState>>,
        time: Res<Time>,
        mut timer: ResMut<SplashTimer>,
    ) {
        if timer.tick(time.delta()).finished() {
            game_state.set(GameState::Menu);
        }
    }
}

mod game {
    use bevy::{
        color::palettes::basic::{BLUE, LIME},
        prelude::*,
    };

    use super::{despawn_screen, DisplayQuality, GameState, Volume, TEXT_COLOR};

    // This plugin will contain the game. In this case, it's just be a screen that will
    // display the current settings for 5 seconds before returning to the menu
    pub fn game_plugin(app: &mut App) {
        app.add_systems(OnEnter(GameState::Game), game_setup)
            .add_systems(Update, game.run_if(in_state(GameState::Game)))
            .add_systems(OnExit(GameState::Game), despawn_screen::<OnGameScreen>);
    }

    // Tag component used to tag entities added on the game screen
    #[derive(Component)]
    struct OnGameScreen;

    #[derive(Resource, Deref, DerefMut)]
    struct GameTimer(Timer);

    fn game_setup(
        mut commands: Commands,
        display_quality: Res<DisplayQuality>,
        volume: Res<Volume>,
    ) {
        commands
            .spawn((
                NodeBundle {
                    style: Style {
                        width: Val::Percent(100.0),
                        height: Val::Percent(100.0),
                        // center children
                        align_items: AlignItems::Center,
                        justify_content: JustifyContent::Center,
                        ..default()
                    },
                    ..default()
                },
                OnGameScreen,
            ))
            .with_children(|parent| {
                // First create a `NodeBundle` for centering what we want to display
                parent
                    .spawn(NodeBundle {
                        style: Style {
                            // This will display its children in a column, from top to bottom
                            flex_direction: FlexDirection::Column,
                            // `align_items` will align children on the cross axis. Here the main axis is
                            // vertical (column), so the cross axis is horizontal. This will center the
                            // children
                            align_items: AlignItems::Center,
                            ..default()
                        },
                        background_color: Color::BLACK.into(),
                        ..default()
                    })
                    .with_children(|parent| {
                        // Display two lines of text, the second one with the current settings
                        parent.spawn(
                            TextBundle::from_section(
                                "Will be back to the menu shortly...",
                                TextStyle {
                                    font_size: 80.0,
                                    color: TEXT_COLOR,
                                    ..default()
                                },
                            )
                            .with_style(Style {
                                margin: UiRect::all(Val::Px(50.0)),
                                ..default()
                            }),
                        );
                        parent.spawn(
                            TextBundle::from_sections([
                                TextSection::new(
                                    format!("quality: {:?}", *display_quality),
                                    TextStyle {
                                        font_size: 60.0,
                                        color: BLUE.into(),
                                        ..default()
                                    },
                                ),
                                TextSection::new(
                                    " - ",
                                    TextStyle {
                                        font_size: 60.0,
                                        color: TEXT_COLOR,
                                        ..default()
                                    },
                                ),
                                TextSection::new(
                                    format!("volume: {:?}", *volume),
                                    TextStyle {
                                        font_size: 60.0,
                                        color: LIME.into(),
                                        ..default()
                                    },
                                ),
                            ])
                            .with_style(Style {
                                margin: UiRect::all(Val::Px(50.0)),
                                ..default()
                            }),
                        );
                    });
            });
        // Spawn a 5 seconds timer to trigger going back to the menu
        commands.insert_resource(GameTimer(Timer::from_seconds(5.0, TimerMode::Once)));
    }

    // Tick the timer, and change state when finished
    fn game(
        time: Res<Time>,
        mut game_state: ResMut<NextState<GameState>>,
        mut timer: ResMut<GameTimer>,
    ) {
        if timer.tick(time.delta()).finished() {
            game_state.set(GameState::Menu);
        }
    }
}

mod menu {
    use bevy::{app::AppExit, color::palettes::css::CRIMSON, prelude::*};

    use super::{despawn_screen, DisplayQuality, GameState, Volume, TEXT_COLOR};

    // This plugin manages the menu, with 5 different screens:
    // - a main menu with "New Game", "Settings", "Quit"
    // - a settings menu with two submenus and a back button
    // - two settings screen with a setting that can be set and a back button
    pub fn menu_plugin(app: &mut App) {
        app
            // At start, the menu is not enabled. This will be changed in `menu_setup` when
            // entering the `GameState::Menu` state.
            // Current screen in the menu is handled by an independent state from `GameState`
            .init_state::<MenuState>()
            .add_systems(OnEnter(GameState::Menu), menu_setup)
            // Systems to handle the main menu screen
            .add_systems(OnEnter(MenuState::Main), main_menu_setup)
            .add_systems(OnExit(MenuState::Main), despawn_screen::<OnMainMenuScreen>)
            // Systems to handle the settings menu screen
            .add_systems(OnEnter(MenuState::Settings), settings_menu_setup)
            .add_systems(
                OnExit(MenuState::Settings),
                despawn_screen::<OnSettingsMenuScreen>,
            )
            // Systems to handle the display settings screen
            .add_systems(
                OnEnter(MenuState::SettingsDisplay),
                display_settings_menu_setup,
            )
            .add_systems(
                Update,
                (setting_button::<DisplayQuality>.run_if(in_state(MenuState::SettingsDisplay)),),
            )
            .add_systems(
                OnExit(MenuState::SettingsDisplay),
                despawn_screen::<OnDisplaySettingsMenuScreen>,
            )
            // Systems to handle the sound settings screen
            .add_systems(OnEnter(MenuState::SettingsSound), sound_settings_menu_setup)
            .add_systems(
                Update,
                setting_button::<Volume>.run_if(in_state(MenuState::SettingsSound)),
            )
            .add_systems(
                OnExit(MenuState::SettingsSound),
                despawn_screen::<OnSoundSettingsMenuScreen>,
            )
            // Common systems to all screens that handles buttons behavior
            .add_systems(
                Update,
                (menu_action, button_system).run_if(in_state(GameState::Menu)),
            );
    }

    // State used for the current menu screen
    #[derive(Clone, Copy, Default, Eq, PartialEq, Debug, Hash, States)]
    enum MenuState {
        Main,
        Settings,
        SettingsDisplay,
        SettingsSound,
        #[default]
        Disabled,
    }

    // Tag component used to tag entities added on the main menu screen
    #[derive(Component)]
    struct OnMainMenuScreen;

    // Tag component used to tag entities added on the settings menu screen
    #[derive(Component)]
    struct OnSettingsMenuScreen;

    // Tag component used to tag entities added on the display settings menu screen
    #[derive(Component)]
    struct OnDisplaySettingsMenuScreen;

    // Tag component used to tag entities added on the sound settings menu screen
    #[derive(Component)]
    struct OnSoundSettingsMenuScreen;

    const NORMAL_BUTTON: Color = Color::srgb(0.15, 0.15, 0.15);
    const HOVERED_BUTTON: Color = Color::srgb(0.25, 0.25, 0.25);
    const HOVERED_PRESSED_BUTTON: Color = Color::srgb(0.25, 0.65, 0.25);
    const PRESSED_BUTTON: Color = Color::srgb(0.35, 0.75, 0.35);

    // Tag component used to mark which setting is currently selected
    #[derive(Component)]
    struct SelectedOption;

    // All actions that can be triggered from a button click
    #[derive(Component)]
    enum MenuButtonAction {
        Play,
        Settings,
        SettingsDisplay,
        SettingsSound,
        BackToMainMenu,
        BackToSettings,
        Quit,
    }

    // This system handles changing all buttons color based on mouse interaction
    fn button_system(
        mut interaction_query: Query<
            (&Interaction, &mut UiImage, Option<&SelectedOption>),
            (Changed<Interaction>, With<Button>),
        >,
    ) {
        for (interaction, mut image, selected) in &mut interaction_query {
            image.color = match (*interaction, selected) {
                (Interaction::Pressed, _) | (Interaction::None, Some(_)) => PRESSED_BUTTON,
                (Interaction::Hovered, Some(_)) => HOVERED_PRESSED_BUTTON,
                (Interaction::Hovered, None) => HOVERED_BUTTON,
                (Interaction::None, None) => NORMAL_BUTTON,
            }
        }
    }

    // This system updates the settings when a new value for a setting is selected, and marks
    // the button as the one currently selected
    fn setting_button<T: Resource + Component + PartialEq + Copy>(
        interaction_query: Query<(&Interaction, &T, Entity), (Changed<Interaction>, With<Button>)>,
        mut selected_query: Query<(Entity, &mut UiImage), With<SelectedOption>>,
        mut commands: Commands,
        mut setting: ResMut<T>,
    ) {
        for (interaction, button_setting, entity) in &interaction_query {
            if *interaction == Interaction::Pressed && *setting != *button_setting {
                let (previous_button, mut previous_image) = selected_query.single_mut();
                previous_image.color = NORMAL_BUTTON;
                commands.entity(previous_button).remove::<SelectedOption>();
                commands.entity(entity).insert(SelectedOption);
                *setting = *button_setting;
            }
        }
    }

    fn menu_setup(mut menu_state: ResMut<NextState<MenuState>>) {
        menu_state.set(MenuState::Main);
    }

    fn main_menu_setup(mut commands: Commands, asset_server: Res<AssetServer>) {
        // Common style for all buttons on the screen
        let button_style = Style {
            width: Val::Px(250.0),
            height: Val::Px(65.0),
            margin: UiRect::all(Val::Px(20.0)),
            justify_content: JustifyContent::Center,
            align_items: AlignItems::Center,
            ..default()
        };
        let button_icon_style = Style {
            width: Val::Px(30.0),
            // This takes the icons out of the flexbox flow, to be positioned exactly
            position_type: PositionType::Absolute,
            // The icon will be close to the left border of the button
            left: Val::Px(10.0),
            ..default()
        };
        let button_text_style = TextStyle {
            font_size: 40.0,
            color: TEXT_COLOR,
            ..default()
        };

        commands
            .spawn((
                NodeBundle {
                    style: Style {
                        width: Val::Percent(100.0),
                        height: Val::Percent(100.0),
                        align_items: AlignItems::Center,
                        justify_content: JustifyContent::Center,
                        ..default()
                    },
                    ..default()
                },
                OnMainMenuScreen,
            ))
            .with_children(|parent| {
                parent
                    .spawn(NodeBundle {
                        style: Style {
                            flex_direction: FlexDirection::Column,
                            align_items: AlignItems::Center,
                            ..default()
                        },
                        background_color: CRIMSON.into(),
                        ..default()
                    })
                    .with_children(|parent| {
                        // Display the game name
                        parent.spawn(
                            TextBundle::from_section(
                                "Bevy Game Menu UI",
                                TextStyle {
                                    font_size: 80.0,
                                    color: TEXT_COLOR,
                                    ..default()
                                },
                            )
                            .with_style(Style {
                                margin: UiRect::all(Val::Px(50.0)),
                                ..default()
                            }),
                        );

                        // Display three buttons for each action available from the main menu:
                        // - new game
                        // - settings
                        // - quit
                        parent
                            .spawn((
                                ButtonBundle {
                                    style: button_style.clone(),
                                    image: UiImage::default().with_color(NORMAL_BUTTON),
                                    ..default()
                                },
                                MenuButtonAction::Play,
                            ))
                            .with_children(|parent| {
                                let icon = asset_server.load("textures/Game Icons/right.png");
                                parent.spawn(ImageBundle {
                                    style: button_icon_style.clone(),
                                    image: UiImage::new(icon),
                                    ..default()
                                });
                                parent.spawn(TextBundle::from_section(
                                    "New Game",
                                    button_text_style.clone(),
                                ));
                            });
                        parent
                            .spawn((
                                ButtonBundle {
                                    style: button_style.clone(),
                                    image: UiImage::default().with_color(NORMAL_BUTTON),
                                    ..default()
                                },
                                MenuButtonAction::Settings,
                            ))
                            .with_children(|parent| {
                                let icon = asset_server.load("textures/Game Icons/wrench.png");
                                parent.spawn(ImageBundle {
                                    style: button_icon_style.clone(),
                                    image: UiImage::new(icon),
                                    ..default()
                                });
                                parent.spawn(TextBundle::from_section(
                                    "Settings",
                                    button_text_style.clone(),
                                ));
                            });
                        parent
                            .spawn((
                                ButtonBundle {
                                    style: button_style,
                                    image: UiImage::default().with_color(NORMAL_BUTTON),
                                    ..default()
                                },
                                MenuButtonAction::Quit,
                            ))
                            .with_children(|parent| {
                                let icon = asset_server.load("textures/Game Icons/exitRight.png");
                                parent.spawn(ImageBundle {
                                    style: button_icon_style,
                                    image: UiImage::new(icon),
                                    ..default()
                                });
                                parent.spawn(TextBundle::from_section("Quit", button_text_style));
                            });
                    });
            });
    }

    fn settings_menu_setup(mut commands: Commands) {
        let button_style = Style {
            width: Val::Px(200.0),
            height: Val::Px(65.0),
            margin: UiRect::all(Val::Px(20.0)),
            justify_content: JustifyContent::Center,
            align_items: AlignItems::Center,
            ..default()
        };

        let button_text_style = TextStyle {
            font_size: 40.0,
            color: TEXT_COLOR,
            ..default()
        };

        commands
            .spawn((
                NodeBundle {
                    style: Style {
                        width: Val::Percent(100.0),
                        height: Val::Percent(100.0),
                        align_items: AlignItems::Center,
                        justify_content: JustifyContent::Center,
                        ..default()
                    },
                    ..default()
                },
                OnSettingsMenuScreen,
            ))
            .with_children(|parent| {
                parent
                    .spawn(NodeBundle {
                        style: Style {
                            flex_direction: FlexDirection::Column,
                            align_items: AlignItems::Center,
                            ..default()
                        },
                        background_color: CRIMSON.into(),
                        ..default()
                    })
                    .with_children(|parent| {
                        for (action, text) in [
                            (MenuButtonAction::SettingsDisplay, "Display"),
                            (MenuButtonAction::SettingsSound, "Sound"),
                            (MenuButtonAction::BackToMainMenu, "Back"),
                        ] {
                            parent
                                .spawn((
                                    ButtonBundle {
                                        style: button_style.clone(),
                                        image: UiImage::default().with_color(NORMAL_BUTTON),
                                        ..default()
                                    },
                                    action,
                                ))
                                .with_children(|parent| {
                                    parent.spawn(TextBundle::from_section(
                                        text,
                                        button_text_style.clone(),
                                    ));
                                });
                        }
                    });
            });
    }

    fn display_settings_menu_setup(mut commands: Commands, display_quality: Res<DisplayQuality>) {
        let button_style = Style {
            width: Val::Px(200.0),
            height: Val::Px(65.0),
            margin: UiRect::all(Val::Px(20.0)),
            justify_content: JustifyContent::Center,
            align_items: AlignItems::Center,
            ..default()
        };
        let button_text_style = TextStyle {
            font_size: 40.0,
            color: TEXT_COLOR,
            ..default()
        };

        commands
            .spawn((
                NodeBundle {
                    style: Style {
                        width: Val::Percent(100.0),
                        height: Val::Percent(100.0),
                        align_items: AlignItems::Center,
                        justify_content: JustifyContent::Center,
                        ..default()
                    },
                    ..default()
                },
                OnDisplaySettingsMenuScreen,
            ))
            .with_children(|parent| {
                parent
                    .spawn(NodeBundle {
                        style: Style {
                            flex_direction: FlexDirection::Column,
                            align_items: AlignItems::Center,
                            ..default()
                        },
                        background_color: CRIMSON.into(),
                        ..default()
                    })
                    .with_children(|parent| {
                        // Create a new `NodeBundle`, this time not setting its `flex_direction`. It will
                        // use the default value, `FlexDirection::Row`, from left to right.
                        parent
                            .spawn(NodeBundle {
                                style: Style {
                                    align_items: AlignItems::Center,
                                    ..default()
                                },
                                background_color: CRIMSON.into(),
                                ..default()
                            })
                            .with_children(|parent| {
                                // Display a label for the current setting
                                parent.spawn(TextBundle::from_section(
                                    "Display Quality",
                                    button_text_style.clone(),
                                ));
                                // Display a button for each possible value
                                for quality_setting in [
                                    DisplayQuality::Low,
                                    DisplayQuality::Medium,
                                    DisplayQuality::High,
                                ] {
                                    let mut entity = parent.spawn((
                                        ButtonBundle {
                                            style: Style {
                                                width: Val::Px(150.0),
                                                height: Val::Px(65.0),
                                                ..button_style.clone()
                                            },
                                            image: UiImage::default().with_color(NORMAL_BUTTON),
                                            ..default()
                                        },
                                        quality_setting,
                                    ));
                                    entity.with_children(|parent| {
                                        parent.spawn(TextBundle::from_section(
                                            format!("{quality_setting:?}"),
                                            button_text_style.clone(),
                                        ));
                                    });
                                    if *display_quality == quality_setting {
                                        entity.insert(SelectedOption);
                                    }
                                }
                            });
                        // Display the back button to return to the settings screen
                        parent
                            .spawn((
                                ButtonBundle {
                                    style: button_style,
                                    image: UiImage::default().with_color(NORMAL_BUTTON),
                                    ..default()
                                },
                                MenuButtonAction::BackToSettings,
                            ))
                            .with_children(|parent| {
                                parent.spawn(TextBundle::from_section("Back", button_text_style));
                            });
                    });
            });
    }

    fn sound_settings_menu_setup(mut commands: Commands, volume: Res<Volume>) {
        let button_style = Style {
            width: Val::Px(200.0),
            height: Val::Px(65.0),
            margin: UiRect::all(Val::Px(20.0)),
            justify_content: JustifyContent::Center,
            align_items: AlignItems::Center,
            ..default()
        };
        let button_text_style = TextStyle {
            font_size: 40.0,
            color: TEXT_COLOR,
            ..default()
        };

        commands
            .spawn((
                NodeBundle {
                    style: Style {
                        width: Val::Percent(100.0),
                        height: Val::Percent(100.0),
                        align_items: AlignItems::Center,
                        justify_content: JustifyContent::Center,
                        ..default()
                    },
                    ..default()
                },
                OnSoundSettingsMenuScreen,
            ))
            .with_children(|parent| {
                parent
                    .spawn(NodeBundle {
                        style: Style {
                            flex_direction: FlexDirection::Column,
                            align_items: AlignItems::Center,
                            ..default()
                        },
                        background_color: CRIMSON.into(),
                        ..default()
                    })
                    .with_children(|parent| {
                        parent
                            .spawn(NodeBundle {
                                style: Style {
                                    align_items: AlignItems::Center,
                                    ..default()
                                },
                                background_color: CRIMSON.into(),
                                ..default()
                            })
                            .with_children(|parent| {
                                parent.spawn(TextBundle::from_section(
                                    "Volume",
                                    button_text_style.clone(),
                                ));
                                for volume_setting in [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] {
                                    let mut entity = parent.spawn((
                                        ButtonBundle {
                                            style: Style {
                                                width: Val::Px(30.0),
                                                height: Val::Px(65.0),
                                                ..button_style.clone()
                                            },
                                            image: UiImage::default().with_color(NORMAL_BUTTON),
                                            ..default()
                                        },
                                        Volume(volume_setting),
                                    ));
                                    if *volume == Volume(volume_setting) {
                                        entity.insert(SelectedOption);
                                    }
                                }
                            });
                        parent
                            .spawn((
                                ButtonBundle {
                                    style: button_style,
                                    image: UiImage::default().with_color(NORMAL_BUTTON),
                                    ..default()
                                },
                                MenuButtonAction::BackToSettings,
                            ))
                            .with_children(|parent| {
                                parent.spawn(TextBundle::from_section("Back", button_text_style));
                            });
                    });
            });
    }

    fn menu_action(
        interaction_query: Query<
            (&Interaction, &MenuButtonAction),
            (Changed<Interaction>, With<Button>),
        >,
        mut app_exit_events: EventWriter<AppExit>,
        mut menu_state: ResMut<NextState<MenuState>>,
        mut game_state: ResMut<NextState<GameState>>,
    ) {
        for (interaction, menu_button_action) in &interaction_query {
            if *interaction == Interaction::Pressed {
                match menu_button_action {
                    MenuButtonAction::Quit => {
                        app_exit_events.send(AppExit::Success);
                    }
                    MenuButtonAction::Play => {
                        game_state.set(GameState::Game);
                        menu_state.set(MenuState::Disabled);
                    }
                    MenuButtonAction::Settings => menu_state.set(MenuState::Settings),
                    MenuButtonAction::SettingsDisplay => {
                        menu_state.set(MenuState::SettingsDisplay);
                    }
                    MenuButtonAction::SettingsSound => {
                        menu_state.set(MenuState::SettingsSound);
                    }
                    MenuButtonAction::BackToMainMenu => menu_state.set(MenuState::Main),
                    MenuButtonAction::BackToSettings => {
                        menu_state.set(MenuState::Settings);
                    }
                }
            }
        }
    }

examples/math/render_primitives.rs (line 320)

fn switch_cameras(current: Res<State<CameraActive>>, mut next: ResMut<NextState<CameraActive>>) {
    let next_state = match current.get() {
        CameraActive::Dim2 => CameraActive::Dim3,
        CameraActive::Dim3 => CameraActive::Dim2,
    };
    next.set(next_state);
}

fn setup_text(
    mut commands: Commands,
    asset_server: Res<AssetServer>,
    cameras: Query<(Entity, &Camera)>,
) {
    let active_camera = cameras
        .iter()
        .find_map(|(entity, camera)| camera.is_active.then_some(entity))
        .expect("run condition ensures existence");
    let text = format!("{text}", text = PrimitiveSelected::default());
    let font_size = 24.0;
    let font: Handle<Font> = asset_server.load("fonts/FiraMono-Medium.ttf");
    let style = TextStyle {
        font,
        font_size,
        color: Color::WHITE,
    };
    let instructions = "Press 'C' to switch between 2D and 3D mode\n\
        Press 'Up' or 'Down' to switch to the next/previous primitive";
    let text = [
        TextSection::new("Primitive: ", style.clone()),
        TextSection::new(text, style.clone()),
        TextSection::new("\n\n", style.clone()),
        TextSection::new(instructions, style.clone()),
        TextSection::new("\n\n", style.clone()),
        TextSection::new(
            "(If nothing is displayed, there's no rendering support yet)",
            style.clone(),
        ),
    ];

    commands
        .spawn((
            HeaderNode,
            NodeBundle {
                style: Style {
                    justify_self: JustifySelf::Center,
                    top: Val::Px(5.0),
                    ..Default::default()
                },
                ..Default::default()
            },
            TargetCamera(active_camera),
        ))
        .with_children(|parent| {
            parent.spawn((
                HeaderText,
                TextBundle::from_sections(text).with_text_justify(JustifyText::Center),
            ));
        });
}

fn update_text(
    primitive_state: Res<State<PrimitiveSelected>>,
    mut header: Query<&mut Text, With<HeaderText>>,
) {
    let new_text = format!("{text}", text = primitive_state.get());
    header.iter_mut().for_each(|mut header_text| {
        if let Some(kind) = header_text.sections.get_mut(1) {
            kind.value.clone_from(&new_text);
        };
    });
}

fn switch_to_next_primitive(
    current: Res<State<PrimitiveSelected>>,
    mut next: ResMut<NextState<PrimitiveSelected>>,
) {
    let next_state = current.get().next();
    next.set(next_state);
}

fn switch_to_previous_primitive(
    current: Res<State<PrimitiveSelected>>,
    mut next: ResMut<NextState<PrimitiveSelected>>,
) {
    let next_state = current.get().previous();
    next.set(next_state);
}

examples/2d/texture_atlas.rs (line 45)

fn check_textures(
    mut next_state: ResMut<NextState<AppState>>,
    rpg_sprite_folder: Res<RpgSpriteFolder>,
    mut events: EventReader<AssetEvent<LoadedFolder>>,
) {
    // Advance the `AppState` once all sprite handles have been loaded by the `AssetServer`
    for event in events.read() {
        if event.is_loaded_with_dependencies(&rpg_sprite_folder.0) {
            next_state.set(AppState::Finished);
        }
    }
}

examples/2d/bounding_2d.rs (line 68)

fn update_test_state(
    keycode: Res<ButtonInput<KeyCode>>,
    cur_state: Res<State<Test>>,
    mut state: ResMut<NextState<Test>>,
) {
    if !keycode.just_pressed(KeyCode::Space) {
        return;
    }

    use Test::*;
    let next = match **cur_state {
        AabbSweep => CircleSweep,
        CircleSweep => RayCast,
        RayCast => AabbCast,
        AabbCast => CircleCast,
        CircleCast => AabbSweep,
    };
    state.set(next);
}

examples/ecs/state.rs (line 106)

fn menu(
    mut next_state: ResMut<NextState<AppState>>,
    mut interaction_query: Query<
        (&Interaction, &mut UiImage),
        (Changed<Interaction>, With<Button>),
    >,
) {
    for (interaction, mut image) in &mut interaction_query {
        match *interaction {
            Interaction::Pressed => {
                image.color = PRESSED_BUTTON;
                next_state.set(AppState::InGame);
            }
            Interaction::Hovered => {
                image.color = HOVERED_BUTTON;
            }
            Interaction::None => {
                image.color = NORMAL_BUTTON;
            }
        }
    }
}

Additional examples can be found in:

• examples/games/alien_cake_addict.rs

Trait Implementations

impl<S> Debug for NextState<S>

where S: Debug + States,

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

Formats the value using the given formatter.

impl<S> Default for NextState<S>

where S: States,

fn default() -> NextState<S>

Returns the “default value” for a type.

impl<S> FromReflect for NextState<S>

where S: States + TypePath, NextState<S>: Any + Send + Sync, Option<S>: FromReflect + TypePath + RegisterForReflection,

fn from_reflect(reflect: &(dyn Reflect + 'static)) -> Option<NextState<S>>

Constructs a concrete instance of Self from a reflected value.

fn take_from_reflect( reflect: Box<dyn Reflect> ) -> Result<Self, Box<dyn Reflect>>

Attempts to downcast the given value to Self using, constructing the value using from_reflect if that fails.

impl<S> GetTypeRegistration for NextState<S>

where S: States + TypePath, NextState<S>: Any + Send + Sync, Option<S>: FromReflect + TypePath + RegisterForReflection,

fn get_type_registration() -> TypeRegistration

Returns the default TypeRegistration for this type.

fn register_type_dependencies(registry: &mut TypeRegistry)

Registers other types needed by this type.

impl<S> Reflect for NextState<S>

where S: States + TypePath, NextState<S>: Any + Send + Sync, Option<S>: FromReflect + TypePath + RegisterForReflection,

fn get_represented_type_info(&self) -> Option<&'static TypeInfo>

Returns the TypeInfo of the type represented by this value.

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

Returns the value as a Box<dyn Any>.

fn as_any(&self) -> &(dyn Any + 'static)

Returns the value as a &dyn Any.

fn as_any_mut(&mut self) -> &mut (dyn Any + 'static)

Returns the value as a &mut dyn Any.

fn into_reflect(self: Box<NextState<S>>) -> Box<dyn Reflect>

Casts this type to a boxed reflected value.

fn as_reflect(&self) -> &(dyn Reflect + 'static)

Casts this type to a reflected value.

fn as_reflect_mut(&mut self) -> &mut (dyn Reflect + 'static)

Casts this type to a mutable reflected value.

fn clone_value(&self) -> Box<dyn Reflect>

Clones the value as a Reflect trait object.

fn set(&mut self, value: Box<dyn Reflect>) -> Result<(), Box<dyn Reflect>>

Performs a type-checked assignment of a reflected value to this value.

fn apply(&mut self, value: &(dyn Reflect + 'static))

Applies a reflected value to this value.

fn reflect_kind(&self) -> ReflectKind

Returns a zero-sized enumeration of “kinds” of type.

fn reflect_ref(&self) -> ReflectRef<'_>

Returns an immutable enumeration of “kinds” of type.

fn reflect_mut(&mut self) -> ReflectMut<'_>

Returns a mutable enumeration of “kinds” of type.

fn reflect_owned(self: Box<NextState<S>>) -> ReflectOwned

Returns an owned enumeration of “kinds” of type.

fn reflect_partial_eq(&self, value: &(dyn Reflect + 'static)) -> Option<bool>

Returns a “partial equality” comparison result.

fn reflect_hash(&self) -> Option<u64>

Returns a hash of the value (which includes the type).

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

Debug formatter for the value.

fn serializable(&self) -> Option<Serializable<'_>>

Returns a serializable version of the value.

fn is_dynamic(&self) -> bool

Indicates whether or not this type is a dynamic type.

impl<S> TupleStruct for NextState<S>

where S: States + TypePath, NextState<S>: Any + Send + Sync, Option<S>: FromReflect + TypePath + RegisterForReflection,

fn field(&self, index: usize) -> Option<&(dyn Reflect + 'static)>

Returns a reference to the value of the field with index index as a &dyn Reflect.

fn field_mut(&mut self, index: usize) -> Option<&mut (dyn Reflect + 'static)>

Returns a mutable reference to the value of the field with index index as a &mut dyn Reflect.

fn field_len(&self) -> usize

Returns the number of fields in the tuple struct.

fn iter_fields(&self) -> TupleStructFieldIter<'_>

Returns an iterator over the values of the tuple struct’s fields.

fn clone_dynamic(&self) -> DynamicTupleStruct

Clones the struct into a DynamicTupleStruct.

impl<S> TypePath for NextState<S>

where S: States + TypePath, NextState<S>: Any + Send + Sync,

fn type_path() -> &'static str

Returns the fully qualified path of the underlying type.

fn short_type_path() -> &'static str

Returns a short, pretty-print enabled path to the type.

fn type_ident() -> Option<&'static str>

Returns the name of the type, or None if it is anonymous.

fn crate_name() -> Option<&'static str>

Returns the name of the crate the type is in, or None if it is anonymous.

fn module_path() -> Option<&'static str>

Returns the path to the module the type is in, or None if it is anonymous.

impl<S> Typed for NextState<S>

where S: States + TypePath, NextState<S>: Any + Send + Sync, Option<S>: FromReflect + TypePath + RegisterForReflection,

fn type_info() -> &'static TypeInfo

Returns the compile-time info for the underlying type.

impl<S> Resource for NextState<S>

where S: States, NextState<S>: Send + Sync + 'static,