Struct bevy_ecs::world::World [−][src]
pub struct World { /* fields omitted */ }
Expand description
Stores and exposes operations on entities, components, resources, and their associated metadata.
Each Entity has a set of components. Each component can have up to one instance of each component type. Entity components can be created, updated, removed, and queried using a given World.
Resources
Worlds can also store resources, which are unique instances of a given type that don’t belong to a specific Entity. There are also non send resources, which can only be accessed on the main thread.
Usage of global resources
- Insert the resource into the
World
, usingWorld::insert_resource
. - Fetch the resource from a system, using
Res
orResMut
.
struct MyResource { value: u32 }
world.insert_resource(MyResource { value: 42 });
fn read_resource_system(resource: Res<MyResource>) {
assert_eq!(resource.value, 42);
}
fn write_resource_system(mut resource: ResMut<MyResource>) {
assert_eq!(resource.value, 42);
resource.value = 0;
assert_eq!(resource.value, 0);
}
Implementations
Retrieves this world’s Entities collection mutably
Retrieves this world’s Archetypes collection
Retrieves this world’s Components collection
Retrieves a mutable reference to this world’s Components collection
Retrieves a WorldCell
, which safely enables multiple mutable World accesses at the same
time, provided those accesses do not conflict with each other.
Retrieves an EntityRef
that exposes read-only operations for the given entity
.
This will panic if the entity
does not exist. Use World::get_entity
if you want
to check for entity existence instead of implicitly panic-ing.
use bevy_ecs::{component::Component, world::World};
#[derive(Component)]
struct Position {
x: f32,
y: f32,
}
let mut world = World::new();
let entity = world.spawn()
.insert(Position { x: 0.0, y: 0.0 })
.id();
let position = world.entity(entity).get::<Position>().unwrap();
assert_eq!(position.x, 0.0);
Retrieves an EntityMut
that exposes read and write operations for the given entity
.
This will panic if the entity
does not exist. Use World::get_entity_mut
if you want
to check for entity existence instead of implicitly panic-ing.
use bevy_ecs::{component::Component, world::World};
#[derive(Component)]
struct Position {
x: f32,
y: f32,
}
let mut world = World::new();
let entity = world.spawn()
.insert(Position { x: 0.0, y: 0.0 })
.id();
let mut position = world.entity_mut(entity).get_mut::<Position>().unwrap();
position.x = 1.0;
Returns an EntityMut
for the given entity
(if it exists) or spawns one if it doesn’t exist.
This will return None
if the entity
exists with a different generation.
Note
Spawning a specific entity
value is rarely the right choice. Most apps should favor World::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).
Retrieves an EntityRef
that exposes read-only operations for the given entity
.
Returns None
if the entity
does not exist. Use World::entity
if you don’t want
to unwrap the EntityRef
yourself.
use bevy_ecs::{component::Component, world::World};
#[derive(Component)]
struct Position {
x: f32,
y: f32,
}
let mut world = World::new();
let entity = world.spawn()
.insert(Position { x: 0.0, y: 0.0 })
.id();
let entity_ref = world.get_entity(entity).unwrap();
let position = entity_ref.get::<Position>().unwrap();
assert_eq!(position.x, 0.0);
Retrieves an EntityMut
that exposes read and write operations for the given entity
.
Returns None
if the entity
does not exist. Use World::entity_mut
if you don’t want
to unwrap the EntityMut
yourself.
use bevy_ecs::{component::Component, world::World};
#[derive(Component)]
struct Position {
x: f32,
y: f32,
}
let mut world = World::new();
let entity = world.spawn()
.insert(Position { x: 0.0, y: 0.0 })
.id();
let mut entity_mut = world.get_entity_mut(entity).unwrap();
let mut position = entity_mut.get_mut::<Position>().unwrap();
position.x = 1.0;
Spawns a new Entity
and returns a corresponding EntityMut
, which can be used
to add components to the entity or retrieve its id.
use bevy_ecs::{component::Component, world::World};
#[derive(Component)]
struct Position {
x: f32,
y: f32,
}
#[derive(Component)]
struct Label(&'static str);
#[derive(Component)]
struct Num(u32);
let mut world = World::new();
let entity = world.spawn()
.insert(Position { x: 0.0, y: 0.0 }) // add a single component
.insert_bundle((Num(1), Label("hello"))) // add a bundle of components
.id();
let position = world.entity(entity).get::<Position>().unwrap();
assert_eq!(position.x, 0.0);
pub fn spawn_batch<I>(&mut self, iter: I) -> SpawnBatchIter<'_, I::IntoIter>ⓘNotable traits for SpawnBatchIter<'_, I>impl<I> Iterator for SpawnBatchIter<'_, I> where
I: Iterator,
I::Item: Bundle, type Item = Entity;
where
I: IntoIterator,
I::Item: Bundle,
pub fn spawn_batch<I>(&mut self, iter: I) -> SpawnBatchIter<'_, I::IntoIter>ⓘNotable traits for SpawnBatchIter<'_, I>impl<I> Iterator for SpawnBatchIter<'_, I> where
I: Iterator,
I::Item: Bundle, type Item = Entity;
where
I: IntoIterator,
I::Item: Bundle,
impl<I> Iterator for SpawnBatchIter<'_, I> where
I: Iterator,
I::Item: Bundle, type Item = Entity;
Spawns a batch of entities with the same component Bundle type. Takes a given Bundle iterator and returns a corresponding Entity iterator. This is more efficient than spawning entities and adding components to them individually, but it is limited to spawning entities with the same Bundle type, whereas spawning individually is more flexible.
use bevy_ecs::{component::Component, entity::Entity, world::World};
#[derive(Component)]
struct Str(&'static str);
#[derive(Component)]
struct Num(u32);
let mut world = World::new();
let entities = world.spawn_batch(vec![
(Str("a"), Num(0)), // the first entity
(Str("b"), Num(1)), // the second entity
]).collect::<Vec<Entity>>();
assert_eq!(entities.len(), 2);
Retrieves a reference to the given entity
’s Component of the given type.
Returns None if the entity
does not have a Component of the given type.
use bevy_ecs::{component::Component, world::World};
#[derive(Component)]
struct Position {
x: f32,
y: f32,
}
let mut world = World::new();
let entity = world.spawn()
.insert(Position { x: 0.0, y: 0.0 })
.id();
let position = world.get::<Position>(entity).unwrap();
assert_eq!(position.x, 0.0);
Retrieves a mutable reference to the given entity
’s Component of the given type.
Returns None if the entity
does not have a Component of the given type.
use bevy_ecs::{component::Component, world::World};
#[derive(Component)]
struct Position {
x: f32,
y: f32,
}
let mut world = World::new();
let entity = world.spawn()
.insert(Position { x: 0.0, y: 0.0 })
.id();
let mut position = world.get_mut::<Position>(entity).unwrap();
position.x = 1.0;
Despawns the given entity
, if it exists. This will also remove all of the entity’s
Components. Returns true
if the entity
is successfully despawned and false
if
the entity
does not exist.
use bevy_ecs::{component::Component, world::World};
#[derive(Component)]
struct Position {
x: f32,
y: f32,
}
let mut world = World::new();
let entity = world.spawn()
.insert(Position { x: 0.0, y: 0.0 })
.id();
assert!(world.despawn(entity));
assert!(world.get_entity(entity).is_none());
assert!(world.get::<Position>(entity).is_none());
Clears component tracker state
Returns QueryState
for the given WorldQuery
, which is used to efficiently
run queries on the World
by storing and reusing the QueryState
.
use bevy_ecs::{component::Component, entity::Entity, world::World};
#[derive(Component, Debug, PartialEq)]
struct Position {
x: f32,
y: f32,
}
#[derive(Component)]
struct Velocity {
x: f32,
y: f32,
}
let mut world = World::new();
let entities = world.spawn_batch(vec![
(Position { x: 0.0, y: 0.0}, Velocity { x: 1.0, y: 0.0 }),
(Position { x: 0.0, y: 0.0}, Velocity { x: 0.0, y: 1.0 }),
]).collect::<Vec<Entity>>();
let mut query = world.query::<(&mut Position, &Velocity)>();
for (mut position, velocity) in query.iter_mut(&mut world) {
position.x += velocity.x;
position.y += velocity.y;
}
assert_eq!(world.get::<Position>(entities[0]).unwrap(), &Position { x: 1.0, y: 0.0 });
assert_eq!(world.get::<Position>(entities[1]).unwrap(), &Position { x: 0.0, y: 1.0 });
To iterate over entities in a deterministic order, sort the results of the query using the desired component as a key. Note that this requires fetching the whole result set from the query and allocation of a Vec to store it.
use bevy_ecs::{component::Component, entity::Entity, world::World};
#[derive(Component, PartialEq, Eq, PartialOrd, Ord, Debug)]
struct Order(i32);
#[derive(Component, PartialEq, Debug)]
struct Label(&'static str);
let mut world = World::new();
let a = world.spawn().insert_bundle((Order(2), Label("second"))).id();
let b = world.spawn().insert_bundle((Order(3), Label("third"))).id();
let c = world.spawn().insert_bundle((Order(1), Label("first"))).id();
let mut entities = world.query::<(Entity, &Order, &Label)>()
.iter(&world)
.collect::<Vec<_>>();
// Sort the query results by their `Order` component before comparing
// to expected results. Query iteration order should not be relied on.
entities.sort_by_key(|e| e.1);
assert_eq!(entities, vec![
(c, &Order(1), &Label("first")),
(a, &Order(2), &Label("second")),
(b, &Order(3), &Label("third")),
]);
pub fn query_filtered<Q: WorldQuery, F: WorldQuery>(
&mut self
) -> QueryState<Q, F> where
F::Fetch: FilterFetch,
pub fn query_filtered<Q: WorldQuery, F: WorldQuery>(
&mut self
) -> QueryState<Q, F> where
F::Fetch: FilterFetch,
Returns QueryState
for the given filtered WorldQuery
, which is used to efficiently
run queries on the World
by storing and reusing the QueryState
.
use bevy_ecs::{component::Component, entity::Entity, world::World, query::With};
#[derive(Component)]
struct A;
#[derive(Component)]
struct B;
let mut world = World::new();
let e1 = world.spawn().insert(A).id();
let e2 = world.spawn().insert_bundle((A, B)).id();
let mut query = world.query_filtered::<Entity, With<B>>();
let matching_entities = query.iter(&world).collect::<Vec<Entity>>();
assert_eq!(matching_entities, vec![e2]);
Returns an iterator of entities that had components of type T
removed
since the last call to World::clear_trackers
.
Returns an iterator of entities that had components with the given component_id
removed
since the last call to World::clear_trackers
.
Inserts a new resource with the given value
.
Resources are “unique” data of a given type.
Inserts a new non-send resource with the given value
.
Resources are “unique” data of a given type.
Removes the resource of a given type and returns it, if it exists. Otherwise returns None. Resources are “unique” data of a given type.
Safety
make sure you’re on main thread if T isn’t Send + Sync
Returns true
if a resource of type T
exists. Otherwise returns false
.
Gets a reference to the resource of the given type, if it exists. Otherwise returns None Resources are “unique” data of a given type.
Gets a mutable reference to the resource of the given type, if it exists. Otherwise returns None Resources are “unique” data of a given type.
pub fn get_resource_or_insert_with<T: Resource>(
&mut self,
func: impl FnOnce() -> T
) -> Mut<'_, T>
pub fn get_resource_or_insert_with<T: Resource>(
&mut self,
func: impl FnOnce() -> T
) -> Mut<'_, T>
Gets a resource of type T
if it exists, otherwise inserts the resource using the result of
calling func
.
Gets a reference to the non-send resource of the given type, if it exists. Otherwise returns None Resources are “unique” data of a given type.
Gets a mutable reference to the non-send resource of the given type, if it exists. Otherwise returns None Resources are “unique” data of a given type.
Gets a mutable reference to the non-send resource of the given type, if it exists. Otherwise returns None Resources are “unique” data of a given type.
Safety
This will allow aliased mutable access to the given non-send resource type. The caller must ensure that only one mutable access exists at a time.
For a given batch of (Entity, Bundle) pairs, either spawns each Entity with the given bundle (if the entity does not exist), or inserts the Bundle (if the entity already exists). This is faster than doing equivalent operations one-by-one. Returns Ok if all entities were successfully inserted into or spawned. Otherwise it returns an Err with a list of entities that could not be spawned or inserted into. A “spawn or insert” operation can only fail if an Entity is passed in with an “invalid generation” that conflicts with an existing Entity.
Note
Spawning a specific entity
value is rarely the right choice. Most apps should use World::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).
use bevy_ecs::{entity::Entity, world::World, component::Component};
#[derive(Component)]
struct A(&'static str);
#[derive(Component, PartialEq, Debug)]
struct B(f32);
let mut world = World::new();
let e0 = world.spawn().id();
let e1 = world.spawn().id();
world.insert_or_spawn_batch(vec![
(e0, (A("a"), B(0.0))), // the first entity
(e1, (A("b"), B(1.0))), // the second entity
]);
assert_eq!(world.get::<B>(e0), Some(&B(0.0)));
Temporarily removes the requested resource from this World, then re-adds it before returning. This enables safe mutable access to a resource while still providing mutable world access
use bevy_ecs::{component::Component, world::{World, Mut}};
#[derive(Component)]
struct A(u32);
#[derive(Component)]
struct B(u32);
let mut world = World::new();
world.insert_resource(A(1));
let entity = world.spawn().insert(B(1)).id();
world.resource_scope(|world, mut a: Mut<A>| {
let b = world.get_mut::<B>(entity).unwrap();
a.0 += b.0;
});
assert_eq!(world.get_resource::<A>().unwrap().0, 2);
Trait Implementations
impl<F> IntoExclusiveSystem<&'_ mut World, ExclusiveSystemFn<F>> for F where
F: FnMut(&mut World) + Send + Sync + 'static,
impl<F> IntoExclusiveSystem<&'_ mut World, ExclusiveSystemFn<F>> for F where
F: FnMut(&mut World) + Send + Sync + 'static,
Auto Trait Implementations
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(where Trait: Downcast
) to Box<dyn Any>
. Box<dyn Any>
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then be further downcast
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. Read more
Convert Rc<Trait>
(where Trait: Downcast
) to Rc<Any>
. Rc<Any>
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. Read more
Convert &Trait
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) to &Any
. This is needed since Rust cannot
generate &Any
’s vtable from &Trait
’s. Read more
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(where Trait: Downcast
) to &Any
. This is needed since Rust cannot
generate &mut Any
’s vtable from &mut Trait
’s. Read more
Creates Self
using data from the given World
Attaches the provided Subscriber
to this type, returning a
WithDispatch
wrapper. Read more
Attaches the current default Subscriber
to this type, returning a
WithDispatch
wrapper. Read more