bevy/crates/bevy_state/src/state_scoped.rs
newclarityex ecccd57417
Generic system config (#17962)
# Objective
Prevents duplicate implementation between IntoSystemConfigs and
IntoSystemSetConfigs using a generic, adds a NodeType trait for more
config flexibility (opening the door to implement
https://github.com/bevyengine/bevy/issues/14195?).

## Solution
Followed writeup by @ItsDoot:
https://hackmd.io/@doot/rJeefFHc1x

Removes IntoSystemConfigs and IntoSystemSetConfigs, instead using
IntoNodeConfigs with generics.

## Testing
Pending

---

## Showcase
N/A

## Migration Guide
SystemSetConfigs -> NodeConfigs<InternedSystemSet>
SystemConfigs -> NodeConfigs<ScheduleSystem>
IntoSystemSetConfigs -> IntoNodeConfigs<InternedSystemSet, M>
IntoSystemConfigs -> IntoNodeConfigs<ScheduleSystem, M>

---------

Co-authored-by: Christian Hughes <9044780+ItsDoot@users.noreply.github.com>
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
2025-03-12 00:12:30 +00:00

94 lines
2.8 KiB
Rust

#[cfg(feature = "bevy_reflect")]
use bevy_ecs::reflect::ReflectComponent;
use bevy_ecs::{
component::Component,
entity::Entity,
event::EventReader,
system::{Commands, Query},
};
#[cfg(feature = "bevy_reflect")]
use bevy_reflect::prelude::*;
use crate::state::{StateTransitionEvent, States};
/// Entities marked with this component will be removed
/// when the world's state of the matching type no longer matches the supplied value.
///
/// To enable this feature remember to add the attribute `#[states(scoped_entities)]` when deriving [`States`].
/// It's also possible to enable it when adding the state to an app with [`enable_state_scoped_entities`](crate::app::AppExtStates::enable_state_scoped_entities).
///
/// ```
/// use bevy_state::prelude::*;
/// use bevy_ecs::prelude::*;
/// use bevy_ecs::system::ScheduleSystem;
///
/// #[derive(Clone, Copy, PartialEq, Eq, Hash, Debug, Default, States)]
/// #[states(scoped_entities)]
/// enum GameState {
/// #[default]
/// MainMenu,
/// SettingsMenu,
/// InGame,
/// }
///
/// # #[derive(Component)]
/// # struct Player;
///
/// fn spawn_player(mut commands: Commands) {
/// commands.spawn((
/// StateScoped(GameState::InGame),
/// Player
/// ));
/// }
///
/// # struct AppMock;
/// # impl AppMock {
/// # fn init_state<S>(&mut self) {}
/// # fn enable_state_scoped_entities<S>(&mut self) {}
/// # fn add_systems<S, M>(&mut self, schedule: S, systems: impl IntoScheduleConfigs<ScheduleSystem, M>) {}
/// # }
/// # struct Update;
/// # let mut app = AppMock;
///
/// app.init_state::<GameState>();
/// app.add_systems(OnEnter(GameState::InGame), spawn_player);
/// ```
#[derive(Component, Clone)]
#[cfg_attr(feature = "bevy_reflect", derive(Reflect), reflect(Component))]
pub struct StateScoped<S: States>(pub S);
impl<S> Default for StateScoped<S>
where
S: States + Default,
{
fn default() -> Self {
Self(S::default())
}
}
/// Removes entities marked with [`StateScoped<S>`]
/// when their state no longer matches the world state.
pub fn clear_state_scoped_entities<S: States>(
mut commands: Commands,
mut transitions: EventReader<StateTransitionEvent<S>>,
query: Query<(Entity, &StateScoped<S>)>,
) {
// We use the latest event, because state machine internals generate at most 1
// transition event (per type) each frame. No event means no change happened
// and we skip iterating all entities.
let Some(transition) = transitions.read().last() else {
return;
};
if transition.entered == transition.exited {
return;
}
let Some(exited) = &transition.exited else {
return;
};
for (entity, binding) in &query {
if binding.0 == *exited {
commands.entity(entity).despawn();
}
}
}