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mod parallel_scope;
use super::{Deferred, IntoObserverSystem, IntoSystem, RegisterSystem, Resource};
use crate::{
self as bevy_ecs,
bundle::Bundle,
component::ComponentId,
entity::{Entities, Entity},
event::Event,
observer::{Observer, TriggerEvent, TriggerTargets},
system::{RunSystemWithInput, SystemId},
world::command_queue::RawCommandQueue,
world::{Command, CommandQueue, EntityWorldMut, FromWorld, World},
};
use bevy_utils::tracing::{error, info};
pub use parallel_scope::*;
use std::marker::PhantomData;
/// A [`Command`] queue to perform structural changes to the [`World`].
///
/// Since each command requires exclusive access to the `World`,
/// all queued commands are automatically applied in sequence
/// when the `apply_deferred` system runs (see [`apply_deferred`] documentation for more details).
///
/// Each command can be used to modify the [`World`] in arbitrary ways:
/// * spawning or despawning entities
/// * inserting components on new or existing entities
/// * inserting resources
/// * etc.
///
/// For a version of [`Commands`] that works in parallel contexts (such as
/// within [`Query::par_iter`](crate::system::Query::par_iter)) see
/// [`ParallelCommands`]
///
/// # Usage
///
/// Add `mut commands: Commands` as a function argument to your system to get a copy of this struct that will be applied the next time a copy of [`apply_deferred`] runs.
/// Commands are almost always used as a [`SystemParam`](crate::system::SystemParam).
///
/// ```
/// # use bevy_ecs::prelude::*;
/// #
/// fn my_system(mut commands: Commands) {
/// // ...
/// }
/// # bevy_ecs::system::assert_is_system(my_system);
/// ```
///
/// # Implementing
///
/// Each built-in command is implemented as a separate method, e.g. [`Commands::spawn`].
/// In addition to the pre-defined command methods, you can add commands with any arbitrary
/// behavior using [`Commands::add`], which accepts any type implementing [`Command`].
///
/// Since closures and other functions implement this trait automatically, this allows one-shot,
/// anonymous custom commands.
///
/// ```
/// # use bevy_ecs::prelude::*;
/// # fn foo(mut commands: Commands) {
/// // NOTE: type inference fails here, so annotations are required on the closure.
/// commands.add(|w: &mut World| {
/// // Mutate the world however you want...
/// # todo!();
/// });
/// # }
/// ```
///
/// [`apply_deferred`]: crate::schedule::apply_deferred
pub struct Commands<'w, 's> {
queue: InternalQueue<'s>,
entities: &'w Entities,
}
// SAFETY: All commands [`Command`] implement [`Send`]
unsafe impl Send for Commands<'_, '_> {}
// SAFETY: `Commands` never gives access to the inner commands.
unsafe impl Sync for Commands<'_, '_> {}
const _: () = {
type __StructFieldsAlias<'w, 's> = (Deferred<'s, CommandQueue>, &'w Entities);
#[doc(hidden)]
pub struct FetchState {
state: <__StructFieldsAlias<'static, 'static> as bevy_ecs::system::SystemParam>::State,
}
// SAFETY: Only reads Entities
unsafe impl bevy_ecs::system::SystemParam for Commands<'_, '_> {
type State = FetchState;
type Item<'w, 's> = Commands<'w, 's>;
fn init_state(
world: &mut bevy_ecs::world::World,
system_meta: &mut bevy_ecs::system::SystemMeta,
) -> Self::State {
FetchState {
state: <__StructFieldsAlias<'_, '_> as bevy_ecs::system::SystemParam>::init_state(
world,
system_meta,
),
}
}
unsafe fn new_archetype(
state: &mut Self::State,
archetype: &bevy_ecs::archetype::Archetype,
system_meta: &mut bevy_ecs::system::SystemMeta,
) {
// SAFETY: Caller guarantees the archetype is from the world used in `init_state`
unsafe {
<__StructFieldsAlias<'_, '_> as bevy_ecs::system::SystemParam>::new_archetype(
&mut state.state,
archetype,
system_meta,
);
};
}
fn apply(
state: &mut Self::State,
system_meta: &bevy_ecs::system::SystemMeta,
world: &mut bevy_ecs::world::World,
) {
<__StructFieldsAlias<'_, '_> as bevy_ecs::system::SystemParam>::apply(
&mut state.state,
system_meta,
world,
);
}
fn queue(
state: &mut Self::State,
system_meta: &bevy_ecs::system::SystemMeta,
world: bevy_ecs::world::DeferredWorld,
) {
<__StructFieldsAlias<'_, '_> as bevy_ecs::system::SystemParam>::queue(
&mut state.state,
system_meta,
world,
);
}
unsafe fn get_param<'w, 's>(
state: &'s mut Self::State,
system_meta: &bevy_ecs::system::SystemMeta,
world: bevy_ecs::world::unsafe_world_cell::UnsafeWorldCell<'w>,
change_tick: bevy_ecs::component::Tick,
) -> Self::Item<'w, 's> {
let(f0,f1,) = <(Deferred<'s,CommandQueue> , &'w Entities,)as bevy_ecs::system::SystemParam> ::get_param(&mut state.state,system_meta,world,change_tick);
Commands {
queue: InternalQueue::CommandQueue(f0),
entities: f1,
}
}
}
// SAFETY: Only reads Entities
unsafe impl<'w, 's> bevy_ecs::system::ReadOnlySystemParam for Commands<'w, 's>
where
Deferred<'s, CommandQueue>: bevy_ecs::system::ReadOnlySystemParam,
&'w Entities: bevy_ecs::system::ReadOnlySystemParam,
{
}
};
enum InternalQueue<'s> {
CommandQueue(Deferred<'s, CommandQueue>),
RawCommandQueue(RawCommandQueue),
}
impl<'w, 's> Commands<'w, 's> {
/// Returns a new `Commands` instance from a [`CommandQueue`] and a [`World`].
///
/// It is not required to call this constructor when using `Commands` as a [system parameter].
///
/// [system parameter]: crate::system::SystemParam
pub fn new(queue: &'s mut CommandQueue, world: &'w World) -> Self {
Self::new_from_entities(queue, &world.entities)
}
/// Returns a new `Commands` instance from a [`CommandQueue`] and an [`Entities`] reference.
///
/// It is not required to call this constructor when using `Commands` as a [system parameter].
///
/// [system parameter]: crate::system::SystemParam
pub fn new_from_entities(queue: &'s mut CommandQueue, entities: &'w Entities) -> Self {
Self {
queue: InternalQueue::CommandQueue(Deferred(queue)),
entities,
}
}
/// Returns a new `Commands` instance from a [`RawCommandQueue`] and an [`Entities`] reference.
///
/// This is used when constructing [`Commands`] from a [`DeferredWorld`](crate::world::DeferredWorld).
///
/// # Safety
///
/// * Caller ensures that `queue` must outlive 'w
pub(crate) unsafe fn new_raw_from_entities(
queue: RawCommandQueue,
entities: &'w Entities,
) -> Self {
Self {
queue: InternalQueue::RawCommandQueue(queue),
entities,
}
}
/// Returns a [`Commands`] with a smaller lifetime.
/// This is useful if you have `&mut Commands` but need `Commands`.
///
/// # Examples
///
/// ```
/// # use bevy_ecs::prelude::*;
/// fn my_system(mut commands: Commands) {
/// // We do our initialization in a separate function,
/// // which expects an owned `Commands`.
/// do_initialization(commands.reborrow());
///
/// // Since we only reborrowed the commands instead of moving them, we can still use them.
/// commands.spawn_empty();
/// }
/// #
/// # fn do_initialization(_: Commands) {}
/// ```
pub fn reborrow(&mut self) -> Commands<'w, '_> {
Commands {
queue: match &mut self.queue {
InternalQueue::CommandQueue(queue) => InternalQueue::CommandQueue(queue.reborrow()),
InternalQueue::RawCommandQueue(queue) => {
InternalQueue::RawCommandQueue(queue.clone())
}
},
entities: self.entities,
}
}
/// Take all commands from `other` and append them to `self`, leaving `other` empty
pub fn append(&mut self, other: &mut CommandQueue) {
match &mut self.queue {
InternalQueue::CommandQueue(queue) => queue.bytes.append(&mut other.bytes),
InternalQueue::RawCommandQueue(queue) => {
// SAFETY: Pointers in `RawCommandQueue` are never null
unsafe { queue.bytes.as_mut() }.append(&mut other.bytes);
}
}
}
/// Pushes a [`Command`] to the queue for creating a new empty [`Entity`],
/// and returns its corresponding [`EntityCommands`].
///
/// See [`World::spawn_empty`] for more details.
///
/// # Example
///
/// ```
/// # use bevy_ecs::prelude::*;
///
/// #[derive(Component)]
/// struct Label(&'static str);
/// #[derive(Component)]
/// struct Strength(u32);
/// #[derive(Component)]
/// struct Agility(u32);
///
/// fn example_system(mut commands: Commands) {
/// // Create a new empty entity and retrieve its id.
/// let empty_entity = commands.spawn_empty().id();
///
/// // Create another empty entity, then add some component to it
/// commands.spawn_empty()
/// // adds a new component bundle to the entity
/// .insert((Strength(1), Agility(2)))
/// // adds a single component to the entity
/// .insert(Label("hello world"));
/// }
/// # bevy_ecs::system::assert_is_system(example_system);
/// ```
///
/// # See also
///
/// - [`spawn`](Self::spawn) to spawn an entity with a bundle.
/// - [`spawn_batch`](Self::spawn_batch) to spawn entities with a bundle each.
pub fn spawn_empty(&mut self) -> EntityCommands {
let entity = self.entities.reserve_entity();
EntityCommands {
entity,
commands: self.reborrow(),
}
}
/// Pushes a [`Command`] to the queue for creating a new [`Entity`] if the given one does not exists,
/// and returns its corresponding [`EntityCommands`].
///
/// This method silently fails by returning [`EntityCommands`]
/// even if the given `Entity` cannot be spawned.
///
/// See [`World::get_or_spawn`] for more details.
///
/// # Note
///
/// Spawning a specific `entity` value is rarely the right choice. Most apps should favor
/// [`Commands::spawn`]. This method should generally only be used for sharing entities across
/// apps, and only when they have a scheme worked out to share an ID space (which doesn't happen
/// by default).
pub fn get_or_spawn(&mut self, entity: Entity) -> EntityCommands {
self.add(move |world: &mut World| {
world.get_or_spawn(entity);
});
EntityCommands {
entity,
commands: self.reborrow(),
}
}
/// Pushes a [`Command`] to the queue for creating a new entity with the given [`Bundle`]'s components,
/// and returns its corresponding [`EntityCommands`].
///
/// # Example
///
/// ```
/// use bevy_ecs::prelude::*;
///
/// #[derive(Component)]
/// struct Component1;
/// #[derive(Component)]
/// struct Component2;
/// #[derive(Component)]
/// struct Label(&'static str);
/// #[derive(Component)]
/// struct Strength(u32);
/// #[derive(Component)]
/// struct Agility(u32);
///
/// #[derive(Bundle)]
/// struct ExampleBundle {
/// a: Component1,
/// b: Component2,
/// }
///
/// fn example_system(mut commands: Commands) {
/// // Create a new entity with a single component.
/// commands.spawn(Component1);
///
/// // Create a new entity with a component bundle.
/// commands.spawn(ExampleBundle {
/// a: Component1,
/// b: Component2,
/// });
///
/// commands
/// // Create a new entity with two components using a "tuple bundle".
/// .spawn((Component1, Component2))
/// // `spawn returns a builder, so you can insert more bundles like this:
/// .insert((Strength(1), Agility(2)))
/// // or insert single components like this:
/// .insert(Label("hello world"));
/// }
/// # bevy_ecs::system::assert_is_system(example_system);
/// ```
///
/// # See also
///
/// - [`spawn_empty`](Self::spawn_empty) to spawn an entity without any components.
/// - [`spawn_batch`](Self::spawn_batch) to spawn entities with a bundle each.
pub fn spawn<T: Bundle>(&mut self, bundle: T) -> EntityCommands {
let mut e = self.spawn_empty();
e.insert(bundle);
e
}
/// Returns the [`EntityCommands`] for the requested [`Entity`].
///
/// # Panics
///
/// This method panics if the requested entity does not exist.
///
/// # Example
///
/// ```
/// use bevy_ecs::prelude::*;
///
/// #[derive(Component)]
/// struct Label(&'static str);
/// #[derive(Component)]
/// struct Strength(u32);
/// #[derive(Component)]
/// struct Agility(u32);
///
/// fn example_system(mut commands: Commands) {
/// // Create a new, empty entity
/// let entity = commands.spawn_empty().id();
///
/// commands.entity(entity)
/// // adds a new component bundle to the entity
/// .insert((Strength(1), Agility(2)))
/// // adds a single component to the entity
/// .insert(Label("hello world"));
/// }
/// # bevy_ecs::system::assert_is_system(example_system);
/// ```
///
/// # See also
///
/// - [`get_entity`](Self::get_entity) for the fallible version.
#[inline]
#[track_caller]
pub fn entity(&mut self, entity: Entity) -> EntityCommands {
#[inline(never)]
#[cold]
#[track_caller]
fn panic_no_entity(entity: Entity) -> ! {
panic!(
"Attempting to create an EntityCommands for entity {entity:?}, which doesn't exist.",
);
}
match self.get_entity(entity) {
Some(entity) => entity,
None => panic_no_entity(entity),
}
}
/// Returns the [`EntityCommands`] for the requested [`Entity`], if it exists.
///
/// Returns `None` if the entity does not exist.
///
/// This method does not guarantee that `EntityCommands` will be successfully applied,
/// since another command in the queue may delete the entity before them.
///
/// # Example
///
/// ```
/// use bevy_ecs::prelude::*;
///
/// #[derive(Component)]
/// struct Label(&'static str);
/// fn example_system(mut commands: Commands) {
/// // Create a new, empty entity
/// let entity = commands.spawn_empty().id();
///
/// // Get the entity if it still exists, which it will in this case
/// if let Some(mut entity_commands) = commands.get_entity(entity) {
/// // adds a single component to the entity
/// entity_commands.insert(Label("hello world"));
/// }
/// }
/// # bevy_ecs::system::assert_is_system(example_system);
/// ```
///
/// # See also
///
/// - [`entity`](Self::entity) for the panicking version.
#[inline]
#[track_caller]
pub fn get_entity(&mut self, entity: Entity) -> Option<EntityCommands> {
self.entities.contains(entity).then_some(EntityCommands {
entity,
commands: self.reborrow(),
})
}
/// Pushes a [`Command`] to the queue for creating entities with a particular [`Bundle`] type.
///
/// `bundles_iter` is a type that can be converted into a [`Bundle`] iterator
/// (it can also be a collection).
///
/// This method is equivalent to iterating `bundles_iter`
/// and calling [`spawn`](Self::spawn) on each bundle,
/// but it is faster due to memory pre-allocation.
///
/// # Example
///
/// ```
/// # use bevy_ecs::prelude::*;
/// #
/// # #[derive(Component)]
/// # struct Name(String);
/// # #[derive(Component)]
/// # struct Score(u32);
/// #
/// # fn system(mut commands: Commands) {
/// commands.spawn_batch(vec![
/// (
/// Name("Alice".to_string()),
/// Score(0),
/// ),
/// (
/// Name("Bob".to_string()),
/// Score(0),
/// ),
/// ]);
/// # }
/// # bevy_ecs::system::assert_is_system(system);
/// ```
///
/// # See also
///
/// - [`spawn`](Self::spawn) to spawn an entity with a bundle.
/// - [`spawn_empty`](Self::spawn_empty) to spawn an entity without any components.
pub fn spawn_batch<I>(&mut self, bundles_iter: I)
where
I: IntoIterator + Send + Sync + 'static,
I::Item: Bundle,
{
self.push(spawn_batch(bundles_iter));
}
/// Push a [`Command`] onto the queue.
pub fn push<C: Command>(&mut self, command: C) {
match &mut self.queue {
InternalQueue::CommandQueue(queue) => {
queue.push(command);
}
InternalQueue::RawCommandQueue(queue) => {
// SAFETY: `RawCommandQueue` is only every constructed in `Commands::new_raw_from_entities`
// where the caller of that has ensured that `queue` outlives `self`
unsafe {
queue.push(command);
}
}
}
}
/// Pushes a [`Command`] to the queue for creating entities, if needed,
/// and for adding a bundle to each entity.
///
/// `bundles_iter` is a type that can be converted into an ([`Entity`], [`Bundle`]) iterator
/// (it can also be a collection).
///
/// When the command is applied,
/// for each (`Entity`, `Bundle`) pair in the given `bundles_iter`,
/// the `Entity` is spawned, if it does not exist already.
/// Then, the `Bundle` is added to the entity.
///
/// This method is equivalent to iterating `bundles_iter`,
/// calling [`get_or_spawn`](Self::get_or_spawn) for each bundle,
/// and passing it to [`insert`](EntityCommands::insert),
/// but it is faster due to memory pre-allocation.
///
/// # Note
///
/// Spawning a specific `entity` value is rarely the right choice. Most apps should use [`Commands::spawn_batch`].
/// This method should generally only be used for sharing entities across apps, and only when they have a scheme
/// worked out to share an ID space (which doesn't happen by default).
pub fn insert_or_spawn_batch<I, B>(&mut self, bundles_iter: I)
where
I: IntoIterator<Item = (Entity, B)> + Send + Sync + 'static,
B: Bundle,
{
self.push(insert_or_spawn_batch(bundles_iter));
}
/// Pushes a [`Command`] to the queue for inserting a [`Resource`] in the [`World`] with an inferred value.
///
/// The inferred value is determined by the [`FromWorld`] trait of the resource.
/// When the command is applied,
/// if the resource already exists, nothing happens.
///
/// See [`World::init_resource`] for more details.
///
/// # Example
///
/// ```
/// # use bevy_ecs::prelude::*;
/// #
/// # #[derive(Resource, Default)]
/// # struct Scoreboard {
/// # current_score: u32,
/// # high_score: u32,
/// # }
/// #
/// # fn initialise_scoreboard(mut commands: Commands) {
/// commands.init_resource::<Scoreboard>();
/// # }
/// # bevy_ecs::system::assert_is_system(initialise_scoreboard);
/// ```
pub fn init_resource<R: Resource + FromWorld>(&mut self) {
self.push(init_resource::<R>);
}
/// Pushes a [`Command`] to the queue for inserting a [`Resource`] in the [`World`] with a specific value.
///
/// This will overwrite any previous value of the same resource type.
///
/// See [`World::insert_resource`] for more details.
///
/// # Example
///
/// ```
/// # use bevy_ecs::prelude::*;
/// #
/// # #[derive(Resource)]
/// # struct Scoreboard {
/// # current_score: u32,
/// # high_score: u32,
/// # }
/// #
/// # fn system(mut commands: Commands) {
/// commands.insert_resource(Scoreboard {
/// current_score: 0,
/// high_score: 0,
/// });
/// # }
/// # bevy_ecs::system::assert_is_system(system);
/// ```
pub fn insert_resource<R: Resource>(&mut self, resource: R) {
self.push(insert_resource(resource));
}
/// Pushes a [`Command`] to the queue for removing a [`Resource`] from the [`World`].
///
/// See [`World::remove_resource`] for more details.
///
/// # Example
///
/// ```
/// # use bevy_ecs::prelude::*;
/// #
/// # #[derive(Resource)]
/// # struct Scoreboard {
/// # current_score: u32,
/// # high_score: u32,
/// # }
/// #
/// # fn system(mut commands: Commands) {
/// commands.remove_resource::<Scoreboard>();
/// # }
/// # bevy_ecs::system::assert_is_system(system);
/// ```
pub fn remove_resource<R: Resource>(&mut self) {
self.push(remove_resource::<R>);
}
/// Runs the system corresponding to the given [`SystemId`].
/// Systems are ran in an exclusive and single threaded way.
/// Running slow systems can become a bottleneck.
///
/// Calls [`World::run_system`](World::run_system).
///
/// There is no way to get the output of a system when run as a command, because the
/// execution of the system happens later. To get the output of a system, use
/// [`World::run_system`] or [`World::run_system_with_input`] instead of running the system as a command.
pub fn run_system(&mut self, id: SystemId) {
self.run_system_with_input(id, ());
}
/// Runs the system corresponding to the given [`SystemId`].
/// Systems are ran in an exclusive and single threaded way.
/// Running slow systems can become a bottleneck.
///
/// Calls [`World::run_system_with_input`](World::run_system_with_input).
///
/// There is no way to get the output of a system when run as a command, because the
/// execution of the system happens later. To get the output of a system, use
/// [`World::run_system`] or [`World::run_system_with_input`] instead of running the system as a command.
pub fn run_system_with_input<I: 'static + Send>(&mut self, id: SystemId<I>, input: I) {
self.push(RunSystemWithInput::new_with_input(id, input));
}
/// Registers a system and returns a [`SystemId`] so it can later be called by [`World::run_system`].
///
/// It's possible to register the same systems more than once, they'll be stored separately.
///
/// This is different from adding systems to a [`Schedule`](crate::schedule::Schedule),
/// because the [`SystemId`] that is returned can be used anywhere in the [`World`] to run the associated system.
/// This allows for running systems in a push-based fashion.
/// Using a [`Schedule`](crate::schedule::Schedule) is still preferred for most cases
/// due to its better performance and ability to run non-conflicting systems simultaneously.
///
/// If you want to prevent Commands from registering the same system multiple times, consider using [`Local`](crate::system::Local)
///
/// # Example
///
/// ```
/// # use bevy_ecs::{prelude::*, world::CommandQueue, system::SystemId};
///
/// #[derive(Resource)]
/// struct Counter(i32);
///
/// fn register_system(mut local_system: Local<Option<SystemId>>, mut commands: Commands) {
/// if let Some(system) = *local_system {
/// commands.run_system(system);
/// } else {
/// *local_system = Some(commands.register_one_shot_system(increment_counter));
/// }
/// }
///
/// fn increment_counter(mut value: ResMut<Counter>) {
/// value.0 += 1;
/// }
///
/// # let mut world = World::default();
/// # world.insert_resource(Counter(0));
/// # let mut queue_1 = CommandQueue::default();
/// # let systemid = {
/// # let mut commands = Commands::new(&mut queue_1, &world);
/// # commands.register_one_shot_system(increment_counter)
/// # };
/// # let mut queue_2 = CommandQueue::default();
/// # {
/// # let mut commands = Commands::new(&mut queue_2, &world);
/// # commands.run_system(systemid);
/// # }
/// # queue_1.append(&mut queue_2);
/// # queue_1.apply(&mut world);
/// # assert_eq!(1, world.resource::<Counter>().0);
/// # bevy_ecs::system::assert_is_system(register_system);
/// ```
pub fn register_one_shot_system<
I: 'static + Send,
O: 'static + Send,
M,
S: IntoSystem<I, O, M> + 'static,
>(
&mut self,
system: S,
) -> SystemId<I, O> {
let entity = self.spawn_empty().id();
self.push(RegisterSystem::new(system, entity));
SystemId::from_entity(entity)
}
/// Pushes a generic [`Command`] to the command queue.
///
/// `command` can be a built-in command, custom struct that implements [`Command`] or a closure
/// that takes [`&mut World`](World) as an argument.
/// # Example
///
/// ```
/// # use bevy_ecs::{world::Command, prelude::*};
/// #[derive(Resource, Default)]
/// struct Counter(u64);
///
/// struct AddToCounter(u64);
///
/// impl Command for AddToCounter {
/// fn apply(self, world: &mut World) {
/// let mut counter = world.get_resource_or_insert_with(Counter::default);
/// counter.0 += self.0;
/// }
/// }
///
/// fn add_three_to_counter_system(mut commands: Commands) {
/// commands.add(AddToCounter(3));
/// }
/// fn add_twenty_five_to_counter_system(mut commands: Commands) {
/// commands.add(|world: &mut World| {
/// let mut counter = world.get_resource_or_insert_with(Counter::default);
/// counter.0 += 25;
/// });
/// }
/// # bevy_ecs::system::assert_is_system(add_three_to_counter_system);
/// # bevy_ecs::system::assert_is_system(add_twenty_five_to_counter_system);
/// ```
pub fn add<C: Command>(&mut self, command: C) {
self.push(command);
}
/// Sends a "global" [`Trigger`] without any targets. This will run any [`Observer`] of the `event` that
/// isn't scoped to specific targets.
pub fn trigger(&mut self, event: impl Event) {
self.add(TriggerEvent { event, targets: () });
}
/// Sends a [`Trigger`] for the given targets. This will run any [`Observer`] of the `event` that
/// watches those targets.
pub fn trigger_targets(&mut self, event: impl Event, targets: impl TriggerTargets) {
self.add(TriggerEvent { event, targets });
}
/// Spawn an [`Observer`] and returns the [`EntityCommands`] associated with the entity that stores the observer.
pub fn observe<E: Event, B: Bundle, M>(
&mut self,
observer: impl IntoObserverSystem<E, B, M>,
) -> EntityCommands {
self.spawn(Observer::new(observer))
}
}
/// A [`Command`] which gets executed for a given [`Entity`].
///
/// # Examples
///
/// ```
/// # use std::collections::HashSet;
/// # use bevy_ecs::prelude::*;
/// use bevy_ecs::system::EntityCommand;
/// #
/// # #[derive(Component, PartialEq)]
/// # struct Name(String);
/// # impl Name {
/// # fn new(s: String) -> Self { Name(s) }
/// # fn as_str(&self) -> &str { &self.0 }
/// # }
///
/// #[derive(Resource, Default)]
/// struct Counter(i64);
///
/// /// A `Command` which names an entity based on a global counter.
/// fn count_name(entity: Entity, world: &mut World) {
/// // Get the current value of the counter, and increment it for next time.
/// let mut counter = world.resource_mut::<Counter>();
/// let i = counter.0;
/// counter.0 += 1;
///
/// // Name the entity after the value of the counter.
/// world.entity_mut(entity).insert(Name::new(format!("Entity #{i}")));
/// }
///
/// // App creation boilerplate omitted...
/// # let mut world = World::new();
/// # world.init_resource::<Counter>();
/// #
/// # let mut setup_schedule = Schedule::default();
/// # setup_schedule.add_systems(setup);
/// # let mut assert_schedule = Schedule::default();
/// # assert_schedule.add_systems(assert_names);
/// #
/// # setup_schedule.run(&mut world);
/// # assert_schedule.run(&mut world);
///
/// fn setup(mut commands: Commands) {
/// commands.spawn_empty().add(count_name);
/// commands.spawn_empty().add(count_name);
/// }
///
/// fn assert_names(named: Query<&Name>) {
/// // We use a HashSet because we do not care about the order.
/// let names: HashSet<_> = named.iter().map(Name::as_str).collect();
/// assert_eq!(names, HashSet::from_iter(["Entity #0", "Entity #1"]));
/// }
/// ```
pub trait EntityCommand<Marker = ()>: Send + 'static {
/// Executes this command for the given [`Entity`].
fn apply(self, id: Entity, world: &mut World);
/// Returns a [`Command`] which executes this [`EntityCommand`] for the given [`Entity`].
#[must_use = "commands do nothing unless applied to a `World`"]
fn with_entity(self, id: Entity) -> WithEntity<Marker, Self>
where
Self: Sized,
{
WithEntity {
cmd: self,
id,
marker: PhantomData,
}
}
}
/// Turns an [`EntityCommand`] type into a [`Command`] type.
pub struct WithEntity<Marker, C: EntityCommand<Marker>> {
cmd: C,
id: Entity,
marker: PhantomData<fn() -> Marker>,
}
impl<M, C: EntityCommand<M>> Command for WithEntity<M, C>
where
M: 'static,
{
#[inline]
fn apply(self, world: &mut World) {
self.cmd.apply(self.id, world);
}
}
/// A list of commands that will be run to modify an [entity](crate::entity).
pub struct EntityCommands<'a> {
pub(crate) entity: Entity,
pub(crate) commands: Commands<'a, 'a>,
}
impl EntityCommands<'_> {
/// Returns the [`Entity`] id of the entity.
///
/// # Example
///
/// ```
/// # use bevy_ecs::prelude::*;
/// #
/// fn my_system(mut commands: Commands) {
/// let entity_id = commands.spawn_empty().id();
/// }
/// # bevy_ecs::system::assert_is_system(my_system);
/// ```
#[inline]
#[must_use = "Omit the .id() call if you do not need to store the `Entity` identifier."]
pub fn id(&self) -> Entity {
self.entity
}
/// Returns an [`EntityCommands`] with a smaller lifetime.
/// This is useful if you have `&mut EntityCommands` but you need `EntityCommands`.
pub fn reborrow(&mut self) -> EntityCommands {
EntityCommands {
entity: self.entity,
commands: self.commands.reborrow(),
}
}
/// Adds a [`Bundle`] of components to the entity.
///
/// This will overwrite any previous value(s) of the same component type.
///
/// # Panics
///
/// The command will panic when applied if the associated entity does not exist.
///
/// To avoid a panic in this case, use the command [`Self::try_insert`] instead.
///
/// # Example
///
/// ```
/// # use bevy_ecs::prelude::*;
/// # #[derive(Resource)]
/// # struct PlayerEntity { entity: Entity }
/// #[derive(Component)]
/// struct Health(u32);
/// #[derive(Component)]
/// struct Strength(u32);
/// #[derive(Component)]
/// struct Defense(u32);
///
/// #[derive(Bundle)]
/// struct CombatBundle {
/// health: Health,
/// strength: Strength,
/// }
///
/// fn add_combat_stats_system(mut commands: Commands, player: Res<PlayerEntity>) {
/// commands
/// .entity(player.entity)
/// // You can insert individual components:
/// .insert(Defense(10))
/// // You can also insert pre-defined bundles of components:
/// .insert(CombatBundle {
/// health: Health(100),
/// strength: Strength(40),
/// })
/// // You can also insert tuples of components and bundles.
/// // This is equivalent to the calls above:
/// .insert((
/// Defense(10),
/// CombatBundle {
/// health: Health(100),
/// strength: Strength(40),
/// },
/// ));
/// }
/// # bevy_ecs::system::assert_is_system(add_combat_stats_system);
/// ```
pub fn insert(&mut self, bundle: impl Bundle) -> &mut Self {
self.add(insert(bundle))
}
/// Tries to add a [`Bundle`] of components to the entity.
///
/// This will overwrite any previous value(s) of the same component type.
///
/// # Note
///
/// Unlike [`Self::insert`], this will not panic if the associated entity does not exist.
///
/// # Example
///
/// ```
/// # use bevy_ecs::prelude::*;
/// # #[derive(Resource)]
/// # struct PlayerEntity { entity: Entity }
/// #[derive(Component)]
/// struct Health(u32);
/// #[derive(Component)]
/// struct Strength(u32);
/// #[derive(Component)]
/// struct Defense(u32);
///
/// #[derive(Bundle)]
/// struct CombatBundle {
/// health: Health,
/// strength: Strength,
/// }
///
/// fn add_combat_stats_system(mut commands: Commands, player: Res<PlayerEntity>) {
/// commands.entity(player.entity)
/// // You can try_insert individual components:
/// .try_insert(Defense(10))
///
/// // You can also insert tuples of components:
/// .try_insert(CombatBundle {
/// health: Health(100),
/// strength: Strength(40),
/// });
///
/// // Suppose this occurs in a parallel adjacent system or process
/// commands.entity(player.entity)
/// .despawn();
///
/// commands.entity(player.entity)
/// // This will not panic nor will it add the component
/// .try_insert(Defense(5));
/// }
/// # bevy_ecs::system::assert_is_system(add_combat_stats_system);
/// ```
pub fn try_insert(&mut self, bundle: impl Bundle) -> &mut Self {
self.add(try_insert(bundle))
}
/// Removes a [`Bundle`] of components from the entity.
///
/// # Example
///
/// ```
/// # use bevy_ecs::prelude::*;
/// #
/// # #[derive(Resource)]
/// # struct PlayerEntity { entity: Entity }
/// #[derive(Component)]
/// struct Health(u32);
/// #[derive(Component)]
/// struct Strength(u32);
/// #[derive(Component)]
/// struct Defense(u32);
///
/// #[derive(Bundle)]
/// struct CombatBundle {
/// health: Health,
/// strength: Strength,
/// }
///
/// fn remove_combat_stats_system(mut commands: Commands, player: Res<PlayerEntity>) {
/// commands
/// .entity(player.entity)
/// // You can remove individual components:
/// .remove::<Defense>()
/// // You can also remove pre-defined Bundles of components:
/// .remove::<CombatBundle>()
/// // You can also remove tuples of components and bundles.
/// // This is equivalent to the calls above:
/// .remove::<(Defense, CombatBundle)>();
/// }
/// # bevy_ecs::system::assert_is_system(remove_combat_stats_system);
/// ```
pub fn remove<T>(&mut self) -> &mut Self
where
T: Bundle,
{
self.add(remove::<T>)
}
/// Removes a component from the entity.
pub fn remove_by_id(&mut self, component_id: ComponentId) -> &mut Self {
self.add(remove_by_id(component_id))
}
/// Removes all components associated with the entity.
pub fn clear(&mut self) -> &mut Self {
self.add(clear())
}
/// Despawns the entity.
/// This will emit a warning if the entity does not exist.
///
/// See [`World::despawn`] for more details.
///
/// # Note
///
/// This won't clean up external references to the entity (such as parent-child relationships
/// if you're using `bevy_hierarchy`), which may leave the world in an invalid state.
///
/// # Example
///
/// ```
/// # use bevy_ecs::prelude::*;
/// #
/// # #[derive(Resource)]
/// # struct CharacterToRemove { entity: Entity }
/// #
/// fn remove_character_system(
/// mut commands: Commands,
/// character_to_remove: Res<CharacterToRemove>
/// )
/// {
/// commands.entity(character_to_remove.entity).despawn();
/// }
/// # bevy_ecs::system::assert_is_system(remove_character_system);
/// ```
pub fn despawn(&mut self) {
self.add(despawn);
}
/// Pushes an [`EntityCommand`] to the queue, which will get executed for the current [`Entity`].
///
/// # Examples
///
/// ```
/// # use bevy_ecs::prelude::*;
/// # fn my_system(mut commands: Commands) {
/// commands
/// .spawn_empty()
/// // Closures with this signature implement `EntityCommand`.
/// .add(|entity: EntityWorldMut| {
/// println!("Executed an EntityCommand for {:?}", entity.id());
/// });
/// # }
/// # bevy_ecs::system::assert_is_system(my_system);
/// ```
pub fn add<M: 'static>(&mut self, command: impl EntityCommand<M>) -> &mut Self {
self.commands.add(command.with_entity(self.entity));
self
}
/// Removes all components except the given [`Bundle`] from the entity.
///
/// This can also be used to remove all the components from the entity by passing it an empty Bundle.
///
/// # Example
///
/// ```
/// # use bevy_ecs::prelude::*;
/// #
/// # #[derive(Resource)]
/// # struct PlayerEntity { entity: Entity }
/// #[derive(Component)]
/// struct Health(u32);
/// #[derive(Component)]
/// struct Strength(u32);
/// #[derive(Component)]
/// struct Defense(u32);
///
/// #[derive(Bundle)]
/// struct CombatBundle {
/// health: Health,
/// strength: Strength,
/// }
///
/// fn remove_combat_stats_system(mut commands: Commands, player: Res<PlayerEntity>) {
/// commands
/// .entity(player.entity)
/// // You can retain a pre-defined Bundle of components,
/// // with this removing only the Defense component
/// .retain::<CombatBundle>()
/// // You can also retain only a single component
/// .retain::<Health>()
/// // And you can remove all the components by passing in an empty Bundle
/// .retain::<()>();
/// }
/// # bevy_ecs::system::assert_is_system(remove_combat_stats_system);
/// ```
pub fn retain<T>(&mut self) -> &mut Self
where
T: Bundle,
{
self.add(retain::<T>)
}
/// Logs the components of the entity at the info level.
///
/// # Panics
///
/// The command will panic when applied if the associated entity does not exist.
pub fn log_components(&mut self) {
self.add(log_components);
}
/// Returns the underlying [`Commands`].
pub fn commands(&mut self) -> Commands {
self.commands.reborrow()
}
/// Creates an [`Observer`](crate::observer::Observer) listening for a trigger of type `T` that targets this entity.
pub fn observe<E: Event, B: Bundle, M>(
&mut self,
system: impl IntoObserverSystem<E, B, M>,
) -> &mut Self {
self.add(observe(system));
self
}
}
impl<F> Command for F
where
F: FnOnce(&mut World) + Send + 'static,
{
fn apply(self, world: &mut World) {
self(world);
}
}
impl<F> EntityCommand<World> for F
where
F: FnOnce(EntityWorldMut) + Send + 'static,
{
fn apply(self, id: Entity, world: &mut World) {
self(world.entity_mut(id));
}
}
impl<F> EntityCommand for F
where
F: FnOnce(Entity, &mut World) + Send + 'static,
{
fn apply(self, id: Entity, world: &mut World) {
self(id, world);
}
}
/// A [`Command`] that consumes an iterator of [`Bundle`]s to spawn a series of entities.
///
/// This is more efficient than spawning the entities individually.
fn spawn_batch<I, B>(bundles_iter: I) -> impl Command
where
I: IntoIterator<Item = B> + Send + Sync + 'static,
B: Bundle,
{
move |world: &mut World| {
world.spawn_batch(bundles_iter);
}
}
/// A [`Command`] that consumes an iterator to add a series of [`Bundle`]s to a set of entities.
/// If any entities do not already exist in the world, they will be spawned.
///
/// This is more efficient than inserting the bundles individually.
fn insert_or_spawn_batch<I, B>(bundles_iter: I) -> impl Command
where
I: IntoIterator<Item = (Entity, B)> + Send + Sync + 'static,
B: Bundle,
{
move |world: &mut World| {
if let Err(invalid_entities) = world.insert_or_spawn_batch(bundles_iter) {
error!(
"Failed to 'insert or spawn' bundle of type {} into the following invalid entities: {:?}",
std::any::type_name::<B>(),
invalid_entities
);
}
}
}
/// A [`Command`] that despawns a specific entity.
/// This will emit a warning if the entity does not exist.
///
/// # Note
///
/// This won't clean up external references to the entity (such as parent-child relationships
/// if you're using `bevy_hierarchy`), which may leave the world in an invalid state.
fn despawn(entity: Entity, world: &mut World) {
world.despawn(entity);
}
/// An [`EntityCommand`] that adds the components in a [`Bundle`] to an entity.
fn insert<T: Bundle>(bundle: T) -> impl EntityCommand {
move |entity: Entity, world: &mut World| {
if let Some(mut entity) = world.get_entity_mut(entity) {
entity.insert(bundle);
} else {
panic!("error[B0003]: Could not insert a bundle (of type `{}`) for entity {:?} because it doesn't exist in this World. See: https://bevyengine.org/learn/errors/#b0003", std::any::type_name::<T>(), entity);
}
}
}
/// An [`EntityCommand`] that attempts to add the components in a [`Bundle`] to an entity.
fn try_insert(bundle: impl Bundle) -> impl EntityCommand {
move |entity, world: &mut World| {
if let Some(mut entity) = world.get_entity_mut(entity) {
entity.insert(bundle);
}
}
}
/// An [`EntityCommand`] that removes components from an entity.
/// For a [`Bundle`] type `T`, this will remove any components in the bundle.
/// Any components in the bundle that aren't found on the entity will be ignored.
fn remove<T: Bundle>(entity: Entity, world: &mut World) {
if let Some(mut entity) = world.get_entity_mut(entity) {
entity.remove::<T>();
}
}
/// An [`EntityCommand`] that removes components with a provided [`ComponentId`] from an entity.
/// # Panics
///
/// Panics if the provided [`ComponentId`] does not exist in the [`World`].
fn remove_by_id(component_id: ComponentId) -> impl EntityCommand {
move |entity: Entity, world: &mut World| {
if let Some(mut entity) = world.get_entity_mut(entity) {
entity.remove_by_id(component_id);
}
}
}
/// An [`EntityCommand`] that removes all components associated with a provided entity.
fn clear() -> impl EntityCommand {
move |entity: Entity, world: &mut World| {
if let Some(mut entity) = world.get_entity_mut(entity) {
entity.clear();
}
}
}
/// An [`EntityCommand`] that removes components from an entity.
/// For a [`Bundle`] type `T`, this will remove all components except those in the bundle.
/// Any components in the bundle that aren't found on the entity will be ignored.
fn retain<T: Bundle>(entity: Entity, world: &mut World) {
if let Some(mut entity_mut) = world.get_entity_mut(entity) {
entity_mut.retain::<T>();
}
}
/// A [`Command`] that inserts a [`Resource`] into the world using a value
/// created with the [`FromWorld`] trait.
fn init_resource<R: Resource + FromWorld>(world: &mut World) {
world.init_resource::<R>();
}
/// A [`Command`] that removes the [resource](Resource) `R` from the world.
fn remove_resource<R: Resource>(world: &mut World) {
world.remove_resource::<R>();
}
/// A [`Command`] that inserts a [`Resource`] into the world.
fn insert_resource<R: Resource>(resource: R) -> impl Command {
move |world: &mut World| {
world.insert_resource(resource);
}
}
/// [`EntityCommand`] to log the components of a given entity. See [`EntityCommands::log_components`].
fn log_components(entity: Entity, world: &mut World) {
let debug_infos: Vec<_> = world
.inspect_entity(entity)
.into_iter()
.map(|component_info| component_info.name())
.collect();
info!("Entity {entity}: {debug_infos:?}");
}
fn observe<E: Event, B: Bundle, M>(
observer: impl IntoObserverSystem<E, B, M>,
) -> impl EntityCommand {
move |entity, world: &mut World| {
if let Some(mut entity) = world.get_entity_mut(entity) {
entity.observe(observer);
}
}
}
#[cfg(test)]
#[allow(clippy::float_cmp, clippy::approx_constant)]
mod tests {
use crate::{
self as bevy_ecs,
component::Component,
system::{Commands, Resource},
world::{CommandQueue, World},
};
use std::{
any::TypeId,
sync::{
atomic::{AtomicUsize, Ordering},
Arc,
},
};
#[allow(dead_code)]
#[derive(Component)]
#[component(storage = "SparseSet")]
struct SparseDropCk(DropCk);
#[derive(Component)]
struct DropCk(Arc<AtomicUsize>);
impl DropCk {
fn new_pair() -> (Self, Arc<AtomicUsize>) {
let atomic = Arc::new(AtomicUsize::new(0));
(DropCk(atomic.clone()), atomic)
}
}
impl Drop for DropCk {
fn drop(&mut self) {
self.0.as_ref().fetch_add(1, Ordering::Relaxed);
}
}
#[derive(Component, Resource)]
struct W<T>(T);
fn simple_command(world: &mut World) {
world.spawn((W(0u32), W(42u64)));
}
#[test]
fn commands() {
let mut world = World::default();
let mut command_queue = CommandQueue::default();
let entity = Commands::new(&mut command_queue, &world)
.spawn((W(1u32), W(2u64)))
.id();
command_queue.apply(&mut world);
assert_eq!(world.entities().len(), 1);
let results = world
.query::<(&W<u32>, &W<u64>)>()
.iter(&world)
.map(|(a, b)| (a.0, b.0))
.collect::<Vec<_>>();
assert_eq!(results, vec![(1u32, 2u64)]);
// test entity despawn
{
let mut commands = Commands::new(&mut command_queue, &world);
commands.entity(entity).despawn();
commands.entity(entity).despawn(); // double despawn shouldn't panic
}
command_queue.apply(&mut world);
let results2 = world
.query::<(&W<u32>, &W<u64>)>()
.iter(&world)
.map(|(a, b)| (a.0, b.0))
.collect::<Vec<_>>();
assert_eq!(results2, vec![]);
// test adding simple (FnOnce) commands
{
let mut commands = Commands::new(&mut command_queue, &world);
// set up a simple command using a closure that adds one additional entity
commands.add(|world: &mut World| {
world.spawn((W(42u32), W(0u64)));
});
// set up a simple command using a function that adds one additional entity
commands.add(simple_command);
}
command_queue.apply(&mut world);
let results3 = world
.query::<(&W<u32>, &W<u64>)>()
.iter(&world)
.map(|(a, b)| (a.0, b.0))
.collect::<Vec<_>>();
assert_eq!(results3, vec![(42u32, 0u64), (0u32, 42u64)]);
}
#[test]
fn remove_components() {
let mut world = World::default();
let mut command_queue = CommandQueue::default();
let (dense_dropck, dense_is_dropped) = DropCk::new_pair();
let (sparse_dropck, sparse_is_dropped) = DropCk::new_pair();
let sparse_dropck = SparseDropCk(sparse_dropck);
let entity = Commands::new(&mut command_queue, &world)
.spawn((W(1u32), W(2u64), dense_dropck, sparse_dropck))
.id();
command_queue.apply(&mut world);
let results_before = world
.query::<(&W<u32>, &W<u64>)>()
.iter(&world)
.map(|(a, b)| (a.0, b.0))
.collect::<Vec<_>>();
assert_eq!(results_before, vec![(1u32, 2u64)]);
// test component removal
Commands::new(&mut command_queue, &world)
.entity(entity)
.remove::<W<u32>>()
.remove::<(W<u32>, W<u64>, SparseDropCk, DropCk)>();
assert_eq!(dense_is_dropped.load(Ordering::Relaxed), 0);
assert_eq!(sparse_is_dropped.load(Ordering::Relaxed), 0);
command_queue.apply(&mut world);
assert_eq!(dense_is_dropped.load(Ordering::Relaxed), 1);
assert_eq!(sparse_is_dropped.load(Ordering::Relaxed), 1);
let results_after = world
.query::<(&W<u32>, &W<u64>)>()
.iter(&world)
.map(|(a, b)| (a.0, b.0))
.collect::<Vec<_>>();
assert_eq!(results_after, vec![]);
let results_after_u64 = world
.query::<&W<u64>>()
.iter(&world)
.map(|v| v.0)
.collect::<Vec<_>>();
assert_eq!(results_after_u64, vec![]);
}
#[test]
fn remove_components_by_id() {
let mut world = World::default();
let mut command_queue = CommandQueue::default();
let (dense_dropck, dense_is_dropped) = DropCk::new_pair();
let (sparse_dropck, sparse_is_dropped) = DropCk::new_pair();
let sparse_dropck = SparseDropCk(sparse_dropck);
let entity = Commands::new(&mut command_queue, &world)
.spawn((W(1u32), W(2u64), dense_dropck, sparse_dropck))
.id();
command_queue.apply(&mut world);
let results_before = world
.query::<(&W<u32>, &W<u64>)>()
.iter(&world)
.map(|(a, b)| (a.0, b.0))
.collect::<Vec<_>>();
assert_eq!(results_before, vec![(1u32, 2u64)]);
// test component removal
Commands::new(&mut command_queue, &world)
.entity(entity)
.remove_by_id(world.components().get_id(TypeId::of::<W<u32>>()).unwrap())
.remove_by_id(world.components().get_id(TypeId::of::<W<u64>>()).unwrap())
.remove_by_id(world.components().get_id(TypeId::of::<DropCk>()).unwrap())
.remove_by_id(
world
.components()
.get_id(TypeId::of::<SparseDropCk>())
.unwrap(),
);
assert_eq!(dense_is_dropped.load(Ordering::Relaxed), 0);
assert_eq!(sparse_is_dropped.load(Ordering::Relaxed), 0);
command_queue.apply(&mut world);
assert_eq!(dense_is_dropped.load(Ordering::Relaxed), 1);
assert_eq!(sparse_is_dropped.load(Ordering::Relaxed), 1);
let results_after = world
.query::<(&W<u32>, &W<u64>)>()
.iter(&world)
.map(|(a, b)| (a.0, b.0))
.collect::<Vec<_>>();
assert_eq!(results_after, vec![]);
let results_after_u64 = world
.query::<&W<u64>>()
.iter(&world)
.map(|v| v.0)
.collect::<Vec<_>>();
assert_eq!(results_after_u64, vec![]);
}
#[test]
fn remove_resources() {
let mut world = World::default();
let mut queue = CommandQueue::default();
{
let mut commands = Commands::new(&mut queue, &world);
commands.insert_resource(W(123i32));
commands.insert_resource(W(456.0f64));
}
queue.apply(&mut world);
assert!(world.contains_resource::<W<i32>>());
assert!(world.contains_resource::<W<f64>>());
{
let mut commands = Commands::new(&mut queue, &world);
// test resource removal
commands.remove_resource::<W<i32>>();
}
queue.apply(&mut world);
assert!(!world.contains_resource::<W<i32>>());
assert!(world.contains_resource::<W<f64>>());
}
fn is_send<T: Send>() {}
fn is_sync<T: Sync>() {}
#[test]
fn test_commands_are_send_and_sync() {
is_send::<Commands>();
is_sync::<Commands>();
}
#[test]
fn append() {
let mut world = World::default();
let mut queue_1 = CommandQueue::default();
{
let mut commands = Commands::new(&mut queue_1, &world);
commands.insert_resource(W(123i32));
}
let mut queue_2 = CommandQueue::default();
{
let mut commands = Commands::new(&mut queue_2, &world);
commands.insert_resource(W(456.0f64));
}
queue_1.append(&mut queue_2);
queue_1.apply(&mut world);
assert!(world.contains_resource::<W<i32>>());
assert!(world.contains_resource::<W<f64>>());
}
}