Add set_state extension method to Commands

crates/bevy_state/src/commands.rs

@@ -0,0 +1,30 @@
+use bevy_ecs::{system::Commands, world::World};
+use bevy_utils::tracing::debug;
+
+use crate::state::{FreelyMutableState, NextState};
+
+/// Extension trait for [`Commands`] adding `bevy_state` helpers.
+pub trait CommandsStatesExt {
+ /// Sets the next state the app should move to.
+ ///
+ /// Internally this schedules a command that updates the [`NextState<S>`](crate::prelude::NextState)
+ /// resource with `state`.
+ ///
+ /// Note that commands introduce sync points to the ECS schedule, so modifying `NextState`
+ /// directly may be more efficient depending on your use-case.
+ fn set_state<S: FreelyMutableState>(&mut self, state: S);
+}
+
+impl CommandsStatesExt for Commands<'_, '_> {
+ fn set_state<S: FreelyMutableState>(&mut self, state: S) {
+ self.add(move |w: &mut World| {
+ let mut next = w.resource_mut::<NextState<S>>();
+ if let NextState::Pending(prev) = &*next {
+ if *prev != state {
+ debug!("overwriting next state {:?} with {:?}", prev, state);
+ }
+ }
+ next.set(state);
+ });
+ }
+}

crates/bevy_state/src/lib.rs

@@ -34,6 +34,8 @@
 #[cfg(feature = "bevy_app")]
 /// Provides [`App`](bevy_app::App) and [`SubApp`](bevy_app::SubApp) with state installation methods
 pub mod app;
+/// Provides extension methods for [`Commands`](bevy_ecs::prelude::Commands).
+pub mod commands;
 /// Provides definitions for the runtime conditions that interact with the state system
 pub mod condition;
 /// Provides definitions for the basic traits required by the state system
@@ -53,6 +55,8 @@ pub mod prelude {
  #[doc(hidden)]
  pub use crate::app::AppExtStates;
  #[doc(hidden)]
+ pub use crate::commands::CommandsStatesExt;
+ #[doc(hidden)]
  pub use crate::condition::*;
  #[cfg(feature = "bevy_reflect")]
  #[doc(hidden)]