Struct bevy_ecs::system::Commands [−][src]
pub struct Commands<'w, 's> { /* fields omitted */ }
Expand description
A list of commands that modify a World
, running at the end of the stage where they
have been invoked.
Usage
Commands
is a SystemParam
, therefore it is declared
as a function parameter:
fn my_system(mut commands: Commands) {
// ...
}
Then, commands can be invoked by calling the methods of commands
.
Implementations
Create a new Commands
from a queue and a world.
Creates a new empty Entity
and returns an EntityCommands
builder for it.
To directly spawn an entity with a Bundle
included, you can use
spawn_bundle
instead of .spawn().insert_bundle()
.
See World::spawn
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().id();
// Create another empty entity, then add some component to it
commands.spawn()
// adds a new component bundle to the entity
.insert_bundle((Strength(1), Agility(2)))
// adds a single component to the entity
.insert(Label("hello world"));
}
Returns an EntityCommands
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
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).
Creates a new entity with the components contained in bundle
.
This returns an EntityCommands
builder, which enables inserting more components and
bundles using a “builder pattern”.
Note that bundle
is a Bundle
, which is a collection of components. Bundle
is
automatically implemented for tuples of components. You can also create your own bundle
types by deriving Bundle
.
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 component bundle.
commands.spawn_bundle(ExampleBundle {
a: Component1,
b: Component2,
});
commands
// Create a new entity with two components using a "tuple bundle".
.spawn_bundle((Component1, Component2))
// spawn_bundle returns a builder, so you can insert more bundles like this:
.insert_bundle((Strength(1), Agility(2)))
// or insert single components like this:
.insert(Label("hello world"));
}
Returns an EntityCommands
builder for the requested Entity
.
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().id();
commands.entity(entity)
// adds a new component bundle to the entity
.insert_bundle((Strength(1), Agility(2)))
// adds a single component to the entity
.insert(Label("hello world"));
}
pub fn spawn_batch<I>(&mut self, bundles_iter: I) where
I: IntoIterator + Send + Sync + 'static,
I::Item: Bundle,
pub fn spawn_batch<I>(&mut self, bundles_iter: I) where
I: IntoIterator + Send + Sync + 'static,
I::Item: Bundle,
Spawns entities to the World
according to the given iterator (or a type that can
be converted to it).
The end result of this command is equivalent to iterating bundles_iter
and calling
spawn
on each bundle, but it is more performant due to memory
pre-allocation.
Example
commands.spawn_batch(vec![
(
Name("Alice".to_string()),
Score(0),
),
(
Name("Bob".to_string()),
Score(0),
),
]);
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.
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).
Inserts a resource to the World
, overwriting any previous value of the same type.
See World::insert_resource
for more details.
Example
commands.insert_resource(Scoreboard {
current_score: 0,
high_score: 0,
});
Removes a resource from the World
.
See World::remove_resource
for more details.
Example
commands.remove_resource::<Scoreboard>();
Adds a command directly to the command list.
Example
use bevy_ecs::system::InsertBundle;
fn add_combat_stats_system(mut commands: Commands, player: Res<PlayerEntity>) {
commands.add(InsertBundle {
entity: player.entity,
bundle: CombatBundle {
health: Health(100),
strength: Strength(40),
defense: Defense(20),
},
});
}
Trait Implementations
type Fetch = CommandQueue
Auto Trait Implementations
impl<'w, 's> RefUnwindSafe for Commands<'w, 's>
impl<'w, 's> !UnwindSafe for Commands<'w, 's>
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) to &Any
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