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Make state private and only accessible through getter for State resource #8009

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merged 6 commits into from
Apr 4, 2023
Merged

Make state private and only accessible through getter for State resource #8009

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e258de8
impl Deref for State<S>
Aceeri Mar 9, 2023
cbbb81d
Privatize the state field so it cant be modified by accident
Aceeri Mar 9, 2023
42d8e34
Getter instead of deref
Aceeri Mar 23, 2023
e94a5fd
Fix up doctest
Aceeri Mar 23, 2023
3b7ec7d
Other doctests
Aceeri Mar 23, 2023
a4b8c16
Impl PartialEq for State<S>
Aceeri Mar 24, 2023
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10 changes: 5 additions & 5 deletions crates/bevy_ecs/src/schedule/condition.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -685,14 +685,14 @@ pub mod common_conditions {
/// app.run(&mut world);
/// assert_eq!(world.resource::<Counter>().0, 1);
///
/// *world.resource_mut::<State<GameState>>() = State(GameState::Paused);
/// *world.resource_mut::<State<GameState>>() = State::new(GameState::Paused);
///
/// // Now that we are in `GameState::Pause`, `pause_system` will run
/// app.run(&mut world);
/// assert_eq!(world.resource::<Counter>().0, 0);
/// ```
pub fn in_state<S: States>(state: S) -> impl FnMut(Res<State<S>>) -> bool + Clone {
move |current_state: Res<State<S>>| current_state.0 == state
move |current_state: Res<State<S>>| *current_state.get() == state
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@cart cart Mar 23, 2023 •
edited
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One more thought / proposal:

  1. Only implement .get() for states that implement copy/clone. Return by value. Then 9/10 times comparisons can be current_state.get() == state
  2. Also implement Deref::deref(), which returns the reference. Use double star (or manual deref() calls) in these cases.

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States has a Clone bound already, so I think it should just return by value 100% of the time.

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I'm not sure I think implicitly cloning for getting the state would be great, I'd be more comfortable with impling on just Copy + Clone ones though.

If we want to simplify this a bit we could just impl PartialEq/Eq on State<S> itself and it could just be
current_state == state

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I like the impl on State quite a bit actually: that really feels like the idiomatic approach.

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Yup way better!

}

/// Generates a [`Condition`](super::Condition)-satisfying closure that returns `true`
Expand Down Expand Up @@ -741,7 +741,7 @@ pub mod common_conditions {
/// app.run(&mut world);
/// assert_eq!(world.resource::<Counter>().0, 1);
///
/// *world.resource_mut::<State<GameState>>() = State(GameState::Paused);
/// *world.resource_mut::<State<GameState>>() = State::new(GameState::Paused);
///
/// // Now that we are in `GameState::Pause`, `pause_system` will run
/// app.run(&mut world);
Expand All @@ -751,7 +751,7 @@ pub mod common_conditions {
state: S,
) -> impl FnMut(Option<Res<State<S>>>) -> bool + Clone {
move |current_state: Option<Res<State<S>>>| match current_state {
Some(current_state) => current_state.0 == state,
Some(current_state) => *current_state.get() == state,
None => false,
}
}
Expand Down Expand Up @@ -803,7 +803,7 @@ pub mod common_conditions {
/// app.run(&mut world);
/// assert_eq!(world.resource::<Counter>().0, 1);
///
/// *world.resource_mut::<State<GameState>>() = State(GameState::Paused);
/// *world.resource_mut::<State<GameState>>() = State::new(GameState::Paused);
///
/// // Now that `GameState` has been updated `my_system` will run
/// app.run(&mut world);
Expand Down
16 changes: 15 additions & 1 deletion crates/bevy_ecs/src/schedule/state.rs
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Expand Up @@ -83,7 +83,21 @@ pub struct OnUpdate<S: States>(pub S);
///
/// The starting state is defined via the [`Default`] implementation for `S`.
#[derive(Resource, Default, Debug)]
pub struct State<S: States>(pub S);
pub struct State<S: States>(S);

impl<S: States> State<S> {
/// Creates a new state with a specific value.
///
/// To change the state use [`NextState<S>`] rather than using this to modify the `State<S>`.
pub fn new(state: S) -> Self {
Self(state)
}

/// Get the current state.
pub fn get(&self) -> &S {
&self.0
}
}

/// The next state of [`State<S>`].
///
Expand Down