use crate::{CoreStage, Plugin, PluginGroup, StartupSchedule, StartupStage};
pub use bevy_derive::AppLabel;
use bevy_ecs::{
event::{Event, Events},
prelude::FromWorld,
schedule::{
IntoSystemDescriptor, Schedule, ShouldRun, Stage, StageLabel, State, StateData, SystemSet,
SystemStage,
},
system::Resource,
world::World,
};
use bevy_utils::{tracing::debug, HashMap, HashSet};
use std::fmt::Debug;
#[cfg(feature = "trace")]
use bevy_utils::tracing::info_span;
bevy_utils::define_label!(
/// A strongly-typed class of labels used to identify an [`App`].
AppLabel,
/// A strongly-typed identifier for an [`AppLabel`].
AppLabelId,
);
/// The [`Resource`] that stores the [`App`]'s [`TypeRegistry`](bevy_reflect::TypeRegistry).
#[cfg(feature = "bevy_reflect")]
#[derive(Resource, Clone, bevy_derive::Deref, bevy_derive::DerefMut, Default)]
pub struct AppTypeRegistry(pub bevy_reflect::TypeRegistryArc);
pub(crate) enum AppError {
DuplicatePlugin { plugin_name: String },
}
#[allow(clippy::needless_doctest_main)]
/// A container of app logic and data.
///
/// Bundles together the necessary elements like [`World`] and [`Schedule`] to create
/// an ECS-based application. It also stores a pointer to a [runner function](Self::set_runner).
/// The runner is responsible for managing the application's event loop and applying the
/// [`Schedule`] to the [`World`] to drive application logic.
///
/// # Examples
///
/// Here is a simple "Hello World" Bevy app:
///
/// ```
/// # use bevy_app::prelude::*;
/// # use bevy_ecs::prelude::*;
/// #
/// fn main() {
/// App::new()
/// .add_system(hello_world_system)
/// .run();
/// }
///
/// fn hello_world_system() {
/// println!("hello world");
/// }
/// ```
pub struct App {
/// The main ECS [`World`] of the [`App`].
/// This stores and provides access to all the main data of the application.
/// The systems of the [`App`] will run using this [`World`].
/// If additional separate [`World`]-[`Schedule`] pairs are needed, you can use [`sub_app`](App::add_sub_app)s.
pub world: World,
/// The [runner function](Self::set_runner) is primarily responsible for managing
/// the application's event loop and advancing the [`Schedule`].
/// Typically, it is not configured manually, but set by one of Bevy's built-in plugins.
/// See `bevy::winit::WinitPlugin` and [`ScheduleRunnerPlugin`](crate::schedule_runner::ScheduleRunnerPlugin).
pub runner: Box<dyn Fn(App)>,
/// A container of [`Stage`]s set to be run in a linear order.
pub schedule: Schedule,
sub_apps: HashMap<AppLabelId, SubApp>,
plugin_registry: Vec<Box<dyn Plugin>>,
plugin_name_added: HashSet<String>,
}
impl Debug for App {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
write!(f, "App {{ sub_apps: ")?;
f.debug_map()
.entries(self.sub_apps.iter().map(|(k, v)| (k, v)))
.finish()?;
write!(f, "}}")
}
}
/// Each `SubApp` has its own [`Schedule`] and [`World`], enabling a separation of concerns.
struct SubApp {
app: App,
runner: Box<dyn Fn(&mut World, &mut App)>,
}
impl Debug for SubApp {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
write!(f, "SubApp {{ app: ")?;
f.debug_map()
.entries(self.app.sub_apps.iter().map(|(k, v)| (k, v)))
.finish()?;
write!(f, "}}")
}
}
impl Default for App {
fn default() -> Self {
let mut app = App::empty();
#[cfg(feature = "bevy_reflect")]
app.init_resource::<AppTypeRegistry>();
app.add_default_stages()
.add_event::<AppExit>()
.add_system_to_stage(CoreStage::Last, World::clear_trackers);
#[cfg(feature = "bevy_ci_testing")]
{
crate::ci_testing::setup_app(&mut app);
}
app
}
}
impl App {
/// Creates a new [`App`] with some default structure to enable core engine features.
/// This is the preferred constructor for most use cases.
pub fn new() -> App {
App::default()
}
/// Creates a new empty [`App`] with minimal default configuration.
///
/// This constructor should be used if you wish to provide a custom schedule, exit handling, cleanup, etc.
pub fn empty() -> App {
Self {
world: Default::default(),
schedule: Default::default(),
runner: Box::new(run_once),
sub_apps: HashMap::default(),
plugin_registry: Vec::default(),
plugin_name_added: Default::default(),
}
}
/// Advances the execution of the [`Schedule`] by one cycle.
///
/// This method also updates sub apps.
///
/// See [`add_sub_app`](Self::add_sub_app) and [`run_once`](Schedule::run_once) for more details.
pub fn update(&mut self) {
#[cfg(feature = "trace")]
let _bevy_frame_update_span = info_span!("frame").entered();
self.schedule.run(&mut self.world);
for sub_app in self.sub_apps.values_mut() {
(sub_app.runner)(&mut self.world, &mut sub_app.app);
}
}
/// Starts the application by calling the app's [runner function](Self::set_runner).
///
/// Finalizes the [`App`] configuration. For general usage, see the example on the item
/// level documentation.
pub fn run(&mut self) {
#[cfg(feature = "trace")]
let _bevy_app_run_span = info_span!("bevy_app").entered();
let mut app = std::mem::replace(self, App::empty());
let runner = std::mem::replace(&mut app.runner, Box::new(run_once));
(runner)(app);
}
/// Adds a [`Stage`] with the given `label` to the last position of the app's
/// [`Schedule`].
///
/// # Examples
///
/// ```
/// # use bevy_app::prelude::*;
/// # use bevy_ecs::prelude::*;
/// # let mut app = App::new();
/// #
/// #[derive(StageLabel)]
/// struct MyStage;
/// app.add_stage(MyStage, SystemStage::parallel());
/// ```
pub fn add_stage<S: Stage>(&mut self, label: impl StageLabel, stage: S) -> &mut Self {
self.schedule.add_stage(label, stage);
self
}
/// Adds a [`Stage`] with the given `label` to the app's [`Schedule`], located
/// immediately after the stage labeled by `target`.
///
/// # Examples
///
/// ```
/// # use bevy_app::prelude::*;
/// # use bevy_ecs::prelude::*;
/// # let mut app = App::new();
/// #
/// #[derive(StageLabel)]
/// struct MyStage;
/// app.add_stage_after(CoreStage::Update, MyStage, SystemStage::parallel());
/// ```
pub fn add_stage_after<S: Stage>(
&mut self,
target: impl StageLabel,
label: impl StageLabel,
stage: S,
) -> &mut Self {
self.schedule.add_stage_after(target, label, stage);
self
}
/// Adds a [`Stage`] with the given `label` to the app's [`Schedule`], located
/// immediately before the stage labeled by `target`.
///
/// # Examples
///
/// ```
/// # use bevy_app::prelude::*;
/// # use bevy_ecs::prelude::*;
/// # let mut app = App::new();
/// #
/// #[derive(StageLabel)]
/// struct MyStage;
/// app.add_stage_before(CoreStage::Update, MyStage, SystemStage::parallel());
/// ```
pub fn add_stage_before<S: Stage>(
&mut self,
target: impl StageLabel,
label: impl StageLabel,
stage: S,
) -> &mut Self {
self.schedule.add_stage_before(target, label, stage);
self
}
/// Adds a [`Stage`] with the given `label` to the last position of the
/// [startup schedule](Self::add_default_stages).
///
/// # Examples
///
/// ```
/// # use bevy_app::prelude::*;
/// # use bevy_ecs::prelude::*;
/// # let mut app = App::new();
/// #
/// #[derive(StageLabel)]
/// struct MyStartupStage;
/// app.add_startup_stage(MyStartupStage, SystemStage::parallel());
/// ```
pub fn add_startup_stage<S: Stage>(&mut self, label: impl StageLabel, stage: S) -> &mut Self {
self.schedule
.stage(StartupSchedule, |schedule: &mut Schedule| {
schedule.add_stage(label, stage)
});
self
}
/// Adds a [startup stage](Self::add_default_stages) with the given `label`, immediately
/// after the stage labeled by `target`.
///
/// The `target` label must refer to a stage inside the startup schedule.
///
/// # Examples
///
/// ```
/// # use bevy_app::prelude::*;
/// # use bevy_ecs::prelude::*;
/// # let mut app = App::new();
/// #
/// #[derive(StageLabel)]
/// struct MyStartupStage;
/// app.add_startup_stage_after(
/// StartupStage::Startup,
/// MyStartupStage,
/// SystemStage::parallel()
/// );
/// ```
pub fn add_startup_stage_after<S: Stage>(
&mut self,
target: impl StageLabel,
label: impl StageLabel,
stage: S,
) -> &mut Self {
self.schedule
.stage(StartupSchedule, |schedule: &mut Schedule| {
schedule.add_stage_after(target, label, stage)
});
self
}
/// Adds a [startup stage](Self::add_default_stages) with the given `label`, immediately
/// before the stage labeled by `target`.
///
/// The `target` label must refer to a stage inside the startup schedule.
///
/// # Examples
///
/// ```
/// # use bevy_app::prelude::*;
/// # use bevy_ecs::prelude::*;
/// # let mut app = App::new();
/// #
/// #[derive(StageLabel)]
/// struct MyStartupStage;
/// app.add_startup_stage_before(
/// StartupStage::Startup,
/// MyStartupStage,
/// SystemStage::parallel()
/// );
/// ```
pub fn add_startup_stage_before<S: Stage>(
&mut self,
target: impl StageLabel,
label: impl StageLabel,
stage: S,
) -> &mut Self {
self.schedule
.stage(StartupSchedule, |schedule: &mut Schedule| {
schedule.add_stage_before(target, label, stage)
});
self
}
/// Fetches the [`Stage`] of type `T` marked with `label` from the [`Schedule`], then
/// executes the provided `func` passing the fetched stage to it as an argument.
///
/// The `func` argument should be a function or a closure that accepts a mutable reference
/// to a struct implementing `Stage` and returns the same type. That means that it should
/// also assume that the stage has already been fetched successfully.
///
/// See [`stage`](Schedule::stage) for more details.
///
/// # Examples
///
/// Here the closure is used to add a system to the update stage:
///
/// ```
/// # use bevy_app::prelude::*;
/// # use bevy_ecs::prelude::*;
/// #
/// # let mut app = App::new();
/// # fn my_system() {}
/// #
/// app.stage(CoreStage::Update, |stage: &mut SystemStage| {
/// stage.add_system(my_system)
/// });
/// ```
pub fn stage<T: Stage, F: FnOnce(&mut T) -> &mut T>(
&mut self,
label: impl StageLabel,
func: F,
) -> &mut Self {
self.schedule.stage(label, func);
self
}
/// Adds a system to the [update stage](Self::add_default_stages) of the app's [`Schedule`].
///
/// Refer to the [system module documentation](bevy_ecs::system) to see how a system
/// can be defined.
///
/// # Examples
///
/// ```
/// # use bevy_app::prelude::*;
/// # use bevy_ecs::prelude::*;
/// #
/// # fn my_system() {}
/// # let mut app = App::new();
/// #
/// app.add_system(my_system);
/// ```
pub fn add_system<Params>(&mut self, system: impl IntoSystemDescriptor<Params>) -> &mut Self {
self.add_system_to_stage(CoreStage::Update, system)
}
/// Adds a [`SystemSet`] to the [update stage](Self::add_default_stages).
///
/// # Examples
///
/// ```
/// # use bevy_app::prelude::*;
/// # use bevy_ecs::prelude::*;
/// #
/// # let mut app = App::new();
/// # fn system_a() {}
/// # fn system_b() {}
/// # fn system_c() {}
/// #
/// app.add_system_set(
/// SystemSet::new()
/// .with_system(system_a)
/// .with_system(system_b)
/// .with_system(system_c),
/// );
/// ```
pub fn add_system_set(&mut self, system_set: SystemSet) -> &mut Self {
self.add_system_set_to_stage(CoreStage::Update, system_set)
}
/// Adds a system to the [`Stage`] identified by `stage_label`.
///
/// # Examples
///
/// ```
/// # use bevy_app::prelude::*;
/// # use bevy_ecs::prelude::*;
/// #
/// # let mut app = App::new();
/// # fn my_system() {}
/// #
/// app.add_system_to_stage(CoreStage::PostUpdate, my_system);
/// ```
pub fn add_system_to_stage<Params>(
&mut self,
stage_label: impl StageLabel,
system: impl IntoSystemDescriptor<Params>,
) -> &mut Self {
use std::any::TypeId;
assert!(
stage_label.type_id() != TypeId::of::<StartupStage>(),
"use `add_startup_system_to_stage` instead of `add_system_to_stage` to add a system to a StartupStage"
);
self.schedule.add_system_to_stage(stage_label, system);
self
}
/// Adds a [`SystemSet`] to the [`Stage`] identified by `stage_label`.
///
/// # Examples
///
/// ```
/// # use bevy_app::prelude::*;
/// # use bevy_ecs::prelude::*;
/// #
/// # let mut app = App::new();
/// # fn system_a() {}
/// # fn system_b() {}
/// # fn system_c() {}
/// #
/// app.add_system_set_to_stage(
/// CoreStage::PostUpdate,
/// SystemSet::new()
/// .with_system(system_a)
/// .with_system(system_b)
/// .with_system(system_c),
/// );
/// ```
pub fn add_system_set_to_stage(
&mut self,
stage_label: impl StageLabel,
system_set: SystemSet,
) -> &mut Self {
use std::any::TypeId;
assert!(
stage_label.type_id() != TypeId::of::<StartupStage>(),
"use `add_startup_system_set_to_stage` instead of `add_system_set_to_stage` to add system sets to a StartupStage"
);
self.schedule
.add_system_set_to_stage(stage_label, system_set);
self
}
/// Adds a system to the [startup stage](Self::add_default_stages) of the app's [`Schedule`].
///
/// * For adding a system that runs every frame, see [`add_system`](Self::add_system).
/// * For adding a system to a specific stage, see [`add_system_to_stage`](Self::add_system_to_stage).
///
/// # Examples
///
/// ```
/// # use bevy_app::prelude::*;
/// # use bevy_ecs::prelude::*;
/// #
/// fn my_startup_system(_commands: Commands) {
/// println!("My startup system");
/// }
///
/// App::new()
/// .add_startup_system(my_startup_system);
/// ```
pub fn add_startup_system<Params>(
&mut self,
system: impl IntoSystemDescriptor<Params>,
) -> &mut Self {
self.add_startup_system_to_stage(StartupStage::Startup, system)
}
/// Adds a [`SystemSet`] to the [startup stage](Self::add_default_stages).
///
/// # Examples
///
/// ```
/// # use bevy_app::prelude::*;
/// # use bevy_ecs::prelude::*;
/// #
/// # let mut app = App::new();
/// # fn startup_system_a() {}
/// # fn startup_system_b() {}
/// # fn startup_system_c() {}
/// #
/// app.add_startup_system_set(
/// SystemSet::new()
/// .with_system(startup_system_a)
/// .with_system(startup_system_b)
/// .with_system(startup_system_c),
/// );
/// ```
pub fn add_startup_system_set(&mut self, system_set: SystemSet) -> &mut Self {
self.add_startup_system_set_to_stage(StartupStage::Startup, system_set)
}
/// Adds a system to the [startup schedule](Self::add_default_stages), in the stage
/// identified by `stage_label`.
///
/// `stage_label` must refer to a stage inside the startup schedule.
///
/// # Examples
///
/// ```
/// # use bevy_app::prelude::*;
/// # use bevy_ecs::prelude::*;
/// #
/// # let mut app = App::new();
/// # fn my_startup_system() {}
/// #
/// app.add_startup_system_to_stage(StartupStage::PreStartup, my_startup_system);
/// ```
pub fn add_startup_system_to_stage<Params>(
&mut self,
stage_label: impl StageLabel,
system: impl IntoSystemDescriptor<Params>,
) -> &mut Self {
self.schedule
.stage(StartupSchedule, |schedule: &mut Schedule| {
schedule.add_system_to_stage(stage_label, system)
});
self
}
/// Adds a [`SystemSet`] to the [startup schedule](Self::add_default_stages), in the stage
/// identified by `stage_label`.
///
/// `stage_label` must refer to a stage inside the startup schedule.
///
/// # Examples
///
/// ```
/// # use bevy_app::prelude::*;
/// # use bevy_ecs::prelude::*;
/// #
/// # let mut app = App::new();
/// # fn startup_system_a() {}
/// # fn startup_system_b() {}
/// # fn startup_system_c() {}
/// #
/// app.add_startup_system_set_to_stage(
/// StartupStage::PreStartup,
/// SystemSet::new()
/// .with_system(startup_system_a)
/// .with_system(startup_system_b)
/// .with_system(startup_system_c),
/// );
/// ```
pub fn add_startup_system_set_to_stage(
&mut self,
stage_label: impl StageLabel,
system_set: SystemSet,
) -> &mut Self {
self.schedule
.stage(StartupSchedule, |schedule: &mut Schedule| {
schedule.add_system_set_to_stage(stage_label, system_set)
});
self
}
/// Adds a new [`State`] with the given `initial` value.
/// This inserts a new `State<T>` resource and adds a new "driver" to [`CoreStage::Update`].
/// Each stage that uses `State<T>` for system run criteria needs a driver. If you need to use
/// your state in a different stage, consider using [`Self::add_state_to_stage`] or manually
/// adding [`State::get_driver`] to additional stages you need it in.
pub fn add_state<T>(&mut self, initial: T) -> &mut Self
where
T: StateData,
{
self.add_state_to_stage(CoreStage::Update, initial)
}
/// Adds a new [`State`] with the given `initial` value.
/// This inserts a new `State<T>` resource and adds a new "driver" to the given stage.
/// Each stage that uses `State<T>` for system run criteria needs a driver. If you need to use
/// your state in more than one stage, consider manually adding [`State::get_driver`] to the
/// stages you need it in.
pub fn add_state_to_stage<T>(&mut self, stage: impl StageLabel, initial: T) -> &mut Self
where
T: StateData,
{
self.insert_resource(State::new(initial))
.add_system_set_to_stage(stage, State::<T>::get_driver())
}
/// Adds utility stages to the [`Schedule`], giving it a standardized structure.
///
/// Adding those stages is necessary to make some core engine features work, like
/// adding systems without specifying a stage, or registering events. This is however
/// done by default by calling `App::default`, which is in turn called by
/// [`App::new`].
///
/// # The stages
///
/// All the added stages, with the exception of the startup stage, run every time the
/// schedule is invoked. The stages are the following, in order of execution:
///
/// - **First:** Runs at the very start of the schedule execution cycle, even before the
/// startup stage.
/// - **Startup:** This is actually a schedule containing sub-stages. Runs only once
/// when the app starts.
/// - **Pre-startup:** Intended for systems that need to run before other startup systems.
/// - **Startup:** The main startup stage. Startup systems are added here by default.
/// - **Post-startup:** Intended for systems that need to run after other startup systems.
/// - **Pre-update:** Often used by plugins to prepare their internal state before the
/// update stage begins.
/// - **Update:** Intended for user defined logic. Systems are added here by default.
/// - **Post-update:** Often used by plugins to finalize their internal state after the
/// world changes that happened during the update stage.
/// - **Last:** Runs right before the end of the schedule execution cycle.
///
/// The labels for those stages are defined in the [`CoreStage`] and [`StartupStage`] `enum`s.
///
/// # Examples
///
/// ```
/// # use bevy_app::prelude::*;
/// #
/// let app = App::empty().add_default_stages();
/// ```
pub fn add_default_stages(&mut self) -> &mut Self {
self.add_stage(CoreStage::First, SystemStage::parallel())
.add_stage(
StartupSchedule,
Schedule::default()
.with_run_criteria(ShouldRun::once)
.with_stage(StartupStage::PreStartup, SystemStage::parallel())
.with_stage(StartupStage::Startup, SystemStage::parallel())
.with_stage(StartupStage::PostStartup, SystemStage::parallel()),
)
.add_stage(CoreStage::PreUpdate, SystemStage::parallel())
.add_stage(CoreStage::Update, SystemStage::parallel())
.add_stage(CoreStage::PostUpdate, SystemStage::parallel())
.add_stage(CoreStage::Last, SystemStage::parallel())
}
/// Setup the application to manage events of type `T`.
///
/// This is done by adding a [`Resource`] of type [`Events::<T>`],
/// and inserting an [`update_system`](Events::update_system) into [`CoreStage::First`].
///
/// See [`Events`] for defining events.
///
/// # Examples
///
/// ```
/// # use bevy_app::prelude::*;
/// # use bevy_ecs::prelude::*;
/// #
/// # struct MyEvent;
/// # let mut app = App::new();
/// #
/// app.add_event::<MyEvent>();
/// ```
pub fn add_event<T>(&mut self) -> &mut Self
where
T: Event,
{
if !self.world.contains_resource::<Events<T>>() {
self.init_resource::<Events<T>>()
.add_system_to_stage(CoreStage::First, Events::<T>::update_system);
}
self
}
/// Inserts a [`Resource`] to the current [`App`] and overwrites any [`Resource`] previously added of the same type.
///
/// A [`Resource`] in Bevy represents globally unique data. [`Resource`]s must be added to Bevy apps
/// before using them. This happens with [`insert_resource`](Self::insert_resource).
///
/// See [`init_resource`](Self::init_resource) for [`Resource`]s that implement [`Default`] or [`FromWorld`].
///
/// # Examples
///
/// ```
/// # use bevy_app::prelude::*;
/// # use bevy_ecs::prelude::*;
/// #
/// #[derive(Resource)]
/// struct MyCounter {
/// counter: usize,
/// }
///
/// App::new()
/// .insert_resource(MyCounter { counter: 0 });
/// ```
pub fn insert_resource<R: Resource>(&mut self, resource: R) -> &mut Self {
self.world.insert_resource(resource);
self
}
/// Inserts a non-send resource to the app.
///
/// You usually want to use [`insert_resource`](Self::insert_resource),
/// but there are some special cases when a resource cannot be sent across threads.
///
/// # Examples
///
/// ```
/// # use bevy_app::prelude::*;
/// # use bevy_ecs::prelude::*;
/// #
/// struct MyCounter {
/// counter: usize,
/// }
///
/// App::new()
/// .insert_non_send_resource(MyCounter { counter: 0 });
/// ```
pub fn insert_non_send_resource<R: 'static>(&mut self, resource: R) -> &mut Self {
self.world.insert_non_send_resource(resource);
self
}
/// Initialize a [`Resource`] with standard starting values by adding it to the [`World`].
///
/// If the [`Resource`] already exists, nothing happens.
///
/// The [`Resource`] must implement the [`FromWorld`] trait.
/// If the [`Default`] trait is implemented, the [`FromWorld`] trait will use
/// the [`Default::default`] method to initialize the [`Resource`].
///
/// # Examples
///
/// ```
/// # use bevy_app::prelude::*;
/// # use bevy_ecs::prelude::*;
/// #
/// #[derive(Resource)]
/// struct MyCounter {
/// counter: usize,
/// }
///
/// impl Default for MyCounter {
/// fn default() -> MyCounter {
/// MyCounter {
/// counter: 100
/// }
/// }
/// }
///
/// App::new()
/// .init_resource::<MyCounter>();
/// ```
pub fn init_resource<R: Resource + FromWorld>(&mut self) -> &mut Self {
self.world.init_resource::<R>();
self
}
/// Initialize a non-send [`Resource`] with standard starting values by adding it to the [`World`].
///
/// The [`Resource`] must implement the [`FromWorld`] trait.
/// If the [`Default`] trait is implemented, the [`FromWorld`] trait will use
/// the [`Default::default`] method to initialize the [`Resource`].
pub fn init_non_send_resource<R: 'static + FromWorld>(&mut self) -> &mut Self {
self.world.init_non_send_resource::<R>();
self
}
/// Sets the function that will be called when the app is run.
///
/// The runner function `run_fn` is called only once by [`App::run`]. If the
/// presence of a main loop in the app is desired, it is the responsibility of the runner
/// function to provide it.
///
/// The runner function is usually not set manually, but by Bevy integrated plugins
/// (e.g. `WinitPlugin`).
///
/// # Examples
///
/// ```
/// # use bevy_app::prelude::*;
/// #
/// fn my_runner(mut app: App) {
/// loop {
/// println!("In main loop");
/// app.update();
/// }
/// }
///
/// App::new()
/// .set_runner(my_runner);
/// ```
pub fn set_runner(&mut self, run_fn: impl Fn(App) + 'static) -> &mut Self {
self.runner = Box::new(run_fn);
self
}
/// Adds a single [`Plugin`].
///
/// One of Bevy's core principles is modularity. All Bevy engine features are implemented
/// as [`Plugin`]s. This includes internal features like the renderer.
///
/// Bevy also provides a few sets of default [`Plugin`]s. See [`add_plugins`](Self::add_plugins).
///
/// # Examples
///
/// ```
/// # use bevy_app::prelude::*;
/// #
/// # // Dummies created to avoid using `bevy_log`,
/// # // which pulls in too many dependencies and breaks rust-analyzer
/// # pub mod bevy_log {
/// # use bevy_app::prelude::*;
/// # #[derive(Default)]
/// # pub struct LogPlugin;
/// # impl Plugin for LogPlugin{
/// # fn build(&self, app: &mut App) {}
/// # }
/// # }
/// App::new().add_plugin(bevy_log::LogPlugin::default());
/// ```
///
/// # Panics
///
/// Panics if the plugin was already added to the application.
pub fn add_plugin<T>(&mut self, plugin: T) -> &mut Self
where
T: Plugin,
{
match self.add_boxed_plugin(Box::new(plugin)) {
Ok(app) => app,
Err(AppError::DuplicatePlugin { plugin_name }) => panic!(
"Error adding plugin {}: : plugin was already added in application",
plugin_name
),
}
}
/// Boxed variant of `add_plugin`, can be used from a [`PluginGroup`]
pub(crate) fn add_boxed_plugin(
&mut self,
plugin: Box<dyn Plugin>,
) -> Result<&mut Self, AppError> {
debug!("added plugin: {}", plugin.name());
if plugin.is_unique() && !self.plugin_name_added.insert(plugin.name().to_string()) {
Err(AppError::DuplicatePlugin {
plugin_name: plugin.name().to_string(),
})?;
}
plugin.build(self);
self.plugin_registry.push(plugin);
Ok(self)
}
/// Checks if a [`Plugin`] has already been added.
///
/// This can be used by plugins to check if a plugin they depend upon has already been
/// added.
pub fn is_plugin_added<T>(&self) -> bool
where
T: Plugin,
{
self.plugin_registry
.iter()
.any(|p| p.downcast_ref::<T>().is_some())
}
/// Returns a vector of references to any plugins of type `T` that have been added.
///
/// This can be used to read the settings of any already added plugins.
/// This vector will be length zero if no plugins of that type have been added.
/// If multiple copies of the same plugin are added to the [`App`], they will be listed in insertion order in this vector.
///
/// ```rust
/// # use bevy_app::prelude::*;
/// # #[derive(Default)]
/// # struct ImagePlugin {
/// # default_sampler: bool,
/// # }
/// # impl Plugin for ImagePlugin {
/// # fn build(&self, app: &mut App) {}
/// # }
/// # let mut app = App::new();
/// # app.add_plugin(ImagePlugin::default());
/// let default_sampler = app.get_added_plugins::<ImagePlugin>()[0].default_sampler;
/// ```
pub fn get_added_plugins<T>(&self) -> Vec<&T>
where
T: Plugin,
{
self.plugin_registry
.iter()
.filter_map(|p| p.downcast_ref())
.collect()
}
/// Adds a group of [`Plugin`]s.
///
/// [`Plugin`]s can be grouped into a set by using a [`PluginGroup`].
///
/// There are built-in [`PluginGroup`]s that provide core engine functionality.
/// The [`PluginGroup`]s available by default are `DefaultPlugins` and `MinimalPlugins`.
///
/// To customize the plugins in the group (reorder, disable a plugin, add a new plugin
/// before / after another plugin), call [`build()`](PluginGroup::build) on the group,
/// which will convert it to a [`PluginGroupBuilder`](crate::PluginGroupBuilder).
///
/// ## Examples
/// ```
/// # use bevy_app::{prelude::*, PluginGroupBuilder, NoopPluginGroup as MinimalPlugins};
/// #
/// App::new()
/// .add_plugins(MinimalPlugins);
/// ```
///
/// # Panics
///
/// Panics if one of the plugin in the group was already added to the application.
pub fn add_plugins<T: PluginGroup>(&mut self, group: T) -> &mut Self {
let builder = group.build();
builder.finish(self);
self
}
/// Registers the type `T` in the [`TypeRegistry`](bevy_reflect::TypeRegistry) resource,
/// adding reflect data as specified in the [`Reflect`](bevy_reflect::Reflect) derive:
/// ```rust,ignore
/// #[derive(Reflect)]
/// #[reflect(Component, Serialize, Deserialize)] // will register ReflectComponent, ReflectSerialize, ReflectDeserialize
/// ```
///
/// See [`bevy_reflect::TypeRegistry::register`].
#[cfg(feature = "bevy_reflect")]
pub fn register_type<T: bevy_reflect::GetTypeRegistration>(&mut self) -> &mut Self {
{
let registry = self.world.resource_mut::<AppTypeRegistry>();
registry.write().register::<T>();
}
self
}
/// Adds the type data `D` to type `T` in the [`TypeRegistry`](bevy_reflect::TypeRegistry) resource.
///
/// Most of the time [`App::register_type`] can be used instead to register a type you derived [`Reflect`](bevy_reflect::Reflect) for.
/// However, in cases where you want to add a piece of type data that was not included in the list of `#[reflect(...)]` type data in the derive,
/// or where the type is generic and cannot register e.g. `ReflectSerialize` unconditionally without knowing the specific type parameters,
/// this method can be used to insert additional type data.
///
/// # Example
/// ```rust
/// use bevy_app::App;
/// use bevy_reflect::{ReflectSerialize, ReflectDeserialize};
///
/// App::new()
/// .register_type::<Option<String>>()
/// .register_type_data::<Option<String>, ReflectSerialize>()
/// .register_type_data::<Option<String>, ReflectDeserialize>();
/// ```
///
/// See [`bevy_reflect::TypeRegistry::register_type_data`].
#[cfg(feature = "bevy_reflect")]
pub fn register_type_data<
T: bevy_reflect::Reflect + 'static,
D: bevy_reflect::TypeData + bevy_reflect::FromType<T>,
>(
&mut self,
) -> &mut Self {
{
let registry = self.world.resource_mut::<AppTypeRegistry>();
registry.write().register_type_data::<T, D>();
}
self
}
/// Adds an [`App`] as a child of the current one.
///
/// The provided function `f` is called by the [`update`](Self::update) method. The [`World`]
/// parameter represents the main app world, while the [`App`] parameter is just a mutable
/// reference to the `SubApp` itself.
pub fn add_sub_app(
&mut self,
label: impl AppLabel,
app: App,
sub_app_runner: impl Fn(&mut World, &mut App) + 'static,
) -> &mut Self {
self.sub_apps.insert(
label.as_label(),
SubApp {
app,
runner: Box::new(sub_app_runner),
},
);
self
}
/// Retrieves a `SubApp` stored inside this [`App`].
///
/// # Panics
///
/// Panics if the `SubApp` doesn't exist.
pub fn sub_app_mut(&mut self, label: impl AppLabel) -> &mut App {
match self.get_sub_app_mut(label) {
Ok(app) => app,
Err(label) => panic!("Sub-App with label '{:?}' does not exist", label.as_str()),
}
}
/// Retrieves a `SubApp` inside this [`App`] with the given label, if it exists. Otherwise returns
/// an [`Err`] containing the given label.
pub fn get_sub_app_mut(&mut self, label: impl AppLabel) -> Result<&mut App, AppLabelId> {
let label = label.as_label();
self.sub_apps
.get_mut(&label)
.map(|sub_app| &mut sub_app.app)
.ok_or(label)
}
/// Retrieves a `SubApp` stored inside this [`App`].
///
/// # Panics
///
/// Panics if the `SubApp` doesn't exist.
pub fn sub_app(&self, label: impl AppLabel) -> &App {
match self.get_sub_app(label) {
Ok(app) => app,
Err(label) => panic!("Sub-App with label '{:?}' does not exist", label.as_str()),
}
}
/// Retrieves a `SubApp` inside this [`App`] with the given label, if it exists. Otherwise returns
/// an [`Err`] containing the given label.
pub fn get_sub_app(&self, label: impl AppLabel) -> Result<&App, impl AppLabel> {
self.sub_apps
.get(&label.as_label())
.map(|sub_app| &sub_app.app)
.ok_or(label)
}
}
fn run_once(mut app: App) {
app.update();
}
/// An event that indicates the [`App`] should exit. This will fully exit the app process at the
/// start of the next tick of the schedule.
///
/// You can also use this event to detect that an exit was requested. In order to receive it, systems
/// subscribing to this event should run after it was emitted and before the schedule of the same
/// frame is over.
#[derive(Debug, Clone, Default)]
pub struct AppExit;
#[cfg(test)]
mod tests {
use crate::{App, Plugin};
struct PluginA;
impl Plugin for PluginA {
fn build(&self, _app: &mut crate::App) {}
}
struct PluginB;
impl Plugin for PluginB {
fn build(&self, _app: &mut crate::App) {}
}
struct PluginC<T>(T);
impl<T: Send + Sync + 'static> Plugin for PluginC<T> {
fn build(&self, _app: &mut crate::App) {}
}
struct PluginD;
impl Plugin for PluginD {
fn build(&self, _app: &mut crate::App) {}
fn is_unique(&self) -> bool {
false
}
}
#[test]
fn can_add_two_plugins() {
App::new().add_plugin(PluginA).add_plugin(PluginB);
}
#[test]
#[should_panic]
fn cant_add_twice_the_same_plugin() {
App::new().add_plugin(PluginA).add_plugin(PluginA);
}
#[test]
fn can_add_twice_the_same_plugin_with_different_type_param() {
App::new().add_plugin(PluginC(0)).add_plugin(PluginC(true));
}
#[test]
fn can_add_twice_the_same_plugin_not_unique() {
App::new().add_plugin(PluginD).add_plugin(PluginD);
}
}