Struct bevy::ecs::world::World

pub struct World { /* private fields */ }

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

1. Insert the resource into the World, using World::insert_resource.
2. Fetch the resource from a system, using Res or ResMut.

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

impl World

pub fn new() -> World

Creates a new empty World

Panics

If usize::MAX Worlds have been created. This guarantee allows System Parameters to safely uniquely identify a World, since its WorldId is unique

pub fn id(&self) -> WorldId

Retrieves this World’s unique ID

pub fn entities(&self) -> &Entities

Retrieves this world’s Entities collection

pub fn entities_mut(&mut self) -> &mut Entities

Retrieves this world’s Entities collection mutably

pub fn archetypes(&self) -> &Archetypes

Retrieves this world’s Archetypes collection

pub fn components(&self) -> &Components

Retrieves this world’s Components collection

pub fn components_mut(&mut self) -> &mut Components

Retrieves a mutable reference to this world’s Components collection

pub fn storages(&self) -> &Storages

Retrieves this world’s Storages collection

pub fn bundles(&self) -> &Bundles

Retrieves this world’s Bundles collection

pub fn cell(&mut self) -> WorldCell<'_>

Retrieves a WorldCell, which safely enables multiple mutable World accesses at the same time, provided those accesses do not conflict with each other.

pub fn init_component<T>(&mut self) -> ComponentId where
    T: Component, 

pub fn entity(&self, entity: Entity) -> EntityRef<'_>

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);

pub fn entity_mut(&mut self, entity: Entity) -> EntityMut<'_>

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;

pub fn get_or_spawn(&mut self, entity: Entity) -> Option<EntityMut<'_>>

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).

pub fn get_entity(&self, entity: Entity) -> Option<EntityRef<'_>>

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);

pub fn get_entity_mut(&mut self, entity: Entity) -> Option<EntityMut<'_>>

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;

pub fn spawn(&mut self) -> EntityMut<'_>

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 as IntoIterator>::IntoIter> where
    I: IntoIterator,
    <I as IntoIterator>::Item: Bundle, 

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);

pub fn get<T>(&self, entity: Entity) -> Option<&T> where
    T: Component, 

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);

pub fn get_mut<T>(&mut self, entity: Entity) -> Option<Mut<'_, T>> where
    T: Component, 

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;

pub fn despawn(&mut self, entity: Entity) -> bool

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());

pub fn clear_trackers(&mut self)

Clears component tracker state

pub fn query<Q>(&mut self) -> QueryState<Q, ()> where
    Q: WorldQuery, 

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, F>(&mut self) -> QueryState<Q, F> where
    Q: WorldQuery,
    F: WorldQuery,
    <F as WorldQuery>::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]);

pub fn removed<T>(&self) -> Cloned<Iter<'_, Entity>> where
    T: Component, 

Returns an iterator of entities that had components of type T removed since the last call to World::clear_trackers.

pub fn removed_with_id(
    &self,
    component_id: ComponentId
) -> Cloned<Iter<'_, Entity>>

Returns an iterator of entities that had components with the given component_id removed since the last call to World::clear_trackers.

pub fn insert_resource<T>(&mut self, value: T) where
    T: Resource, 

Inserts a new resource with the given value. Resources are “unique” data of a given type.

pub fn insert_non_send<T>(&mut self, value: T) where
    T: 'static, 

Inserts a new non-send resource with the given value. Resources are “unique” data of a given type.

pub fn remove_resource<T>(&mut self) -> Option<T> where
    T: Resource, 

Removes the resource of a given type and returns it, if it exists. Otherwise returns None. Resources are “unique” data of a given type.

pub fn remove_non_send<T>(&mut self) -> Option<T> where
    T: 'static, 

pub unsafe fn remove_resource_unchecked<T>(&mut self) -> Option<T> where
    T: 'static, 

Safety

make sure you’re on main thread if T isn’t Send + Sync

pub fn contains_resource<T>(&self) -> bool where
    T: Resource, 

Returns true if a resource of type T exists. Otherwise returns false.

pub fn get_resource<T>(&self) -> Option<&T> where
    T: Resource, 

Gets a reference to the resource of the given type, if it exists. Otherwise returns None Resources are “unique” data of a given type.

pub fn is_resource_added<T>(&self) -> bool where
    T: Resource, 

pub fn is_resource_changed<T>(&self) -> bool where
    T: Resource, 

pub fn get_resource_mut<T>(&mut self) -> Option<Mut<'_, T>> where
    T: Resource, 

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>(
    &mut self,
    func: impl FnOnce() -> T
) -> Mut<'_, T> where
    T: Resource, 

Gets a resource of type T if it exists, otherwise inserts the resource using the result of calling func.

pub unsafe fn get_resource_unchecked_mut<T>(&self) -> Option<Mut<'_, T>> where
    T: Resource, 

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.

Safety

This will allow aliased mutable access to the given resource type. The caller must ensure that only one mutable access exists at a time.

pub fn get_non_send_resource<T>(&self) -> Option<&T> where
    T: 'static, 

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.

pub fn get_non_send_resource_mut<T>(&mut self) -> Option<Mut<'_, T>> where
    T: 'static, 

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.

pub unsafe fn get_non_send_resource_unchecked_mut<T>(
    &self
) -> Option<Mut<'_, T>> where
    T: 'static, 

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.

pub fn insert_or_spawn_batch<I, B>(
    &mut self,
    iter: I
) -> Result<(), Vec<Entity, Global>> where
    I: IntoIterator,
    B: Bundle,
    <I as IntoIterator>::IntoIter: Iterator,
    <<I as IntoIterator>::IntoIter as Iterator>::Item == (Entity, B), 

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)));

pub fn resource_scope<T, U>(
    &mut self,
    f: impl FnOnce(&mut World, Mut<'_, T>) -> U
) -> U where
    T: Resource, 

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);

pub fn increment_change_tick(&self) -> u32

pub fn read_change_tick(&self) -> u32

pub fn change_tick(&mut self) -> u32

pub fn last_change_tick(&self) -> u32

pub fn check_change_ticks(&mut self)

pub fn clear_entities(&mut self)

Trait Implementations

impl Debug for World

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

Formats the value using the given formatter.

impl Default for World

pub fn default() -> World

Returns the “default value” for a type.

impl<F> IntoExclusiveSystem<&'_ mut World, ExclusiveSystemFn<F>> for F where
    F: 'static + FnMut(&mut World) + Send + Sync, 

pub fn exclusive_system(self) -> ExclusiveSystemFn<F>

impl Send for World

impl Sync for World