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https://github.com/bevyengine/bevy
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01aedc8431
# Objective Now that we can consolidate Bundles and Components under a single insert (thanks to #2975 and #6039), almost 100% of world spawns now look like `world.spawn().insert((Some, Tuple, Here))`. Spawning an entity without any components is an extremely uncommon pattern, so it makes sense to give spawn the "first class" ergonomic api. This consolidated api should be made consistent across all spawn apis (such as World and Commands). ## Solution All `spawn` apis (`World::spawn`, `Commands:;spawn`, `ChildBuilder::spawn`, and `WorldChildBuilder::spawn`) now accept a bundle as input: ```rust // before: commands .spawn() .insert((A, B, C)); world .spawn() .insert((A, B, C); // after commands.spawn((A, B, C)); world.spawn((A, B, C)); ``` All existing instances of `spawn_bundle` have been deprecated in favor of the new `spawn` api. A new `spawn_empty` has been added, replacing the old `spawn` api. By allowing `world.spawn(some_bundle)` to replace `world.spawn().insert(some_bundle)`, this opened the door to removing the initial entity allocation in the "empty" archetype / table done in `spawn()` (and subsequent move to the actual archetype in `.insert(some_bundle)`). This improves spawn performance by over 10%:  To take this measurement, I added a new `world_spawn` benchmark. Unfortunately, optimizing `Commands::spawn` is slightly less trivial, as Commands expose the Entity id of spawned entities prior to actually spawning. Doing the optimization would (naively) require assurances that the `spawn(some_bundle)` command is applied before all other commands involving the entity (which would not necessarily be true, if memory serves). Optimizing `Commands::spawn` this way does feel possible, but it will require careful thought (and maybe some additional checks), which deserves its own PR. For now, it has the same performance characteristics of the current `Commands::spawn_bundle` on main. **Note that 99% of this PR is simple renames and refactors. The only code that needs careful scrutiny is the new `World::spawn()` impl, which is relatively straightforward, but it has some new unsafe code (which re-uses battle tested BundlerSpawner code path).** --- ## Changelog - All `spawn` apis (`World::spawn`, `Commands:;spawn`, `ChildBuilder::spawn`, and `WorldChildBuilder::spawn`) now accept a bundle as input - All instances of `spawn_bundle` have been deprecated in favor of the new `spawn` api - World and Commands now have `spawn_empty()`, which is equivalent to the old `spawn()` behavior. ## Migration Guide ```rust // Old (0.8): commands .spawn() .insert_bundle((A, B, C)); // New (0.9) commands.spawn((A, B, C)); // Old (0.8): commands.spawn_bundle((A, B, C)); // New (0.9) commands.spawn((A, B, C)); // Old (0.8): let entity = commands.spawn().id(); // New (0.9) let entity = commands.spawn_empty().id(); // Old (0.8) let entity = world.spawn().id(); // New (0.9) let entity = world.spawn_empty(); ```
89 lines
2.9 KiB
Rust
89 lines
2.9 KiB
Rust
//! Generic types allow us to reuse logic across many related systems,
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//! allowing us to specialize our function's behavior based on which type (or types) are passed in.
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//!
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//! This is commonly useful for working on related components or resources,
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//! where we want to have unique types for querying purposes but want them all to work the same way.
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//! This is particularly powerful when combined with user-defined traits to add more functionality to these related types.
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//! Remember to insert a specialized copy of the system into the schedule for each type that you want to operate on!
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//!
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//! For more advice on working with generic types in Rust, check out <https://doc.rust-lang.org/book/ch10-01-syntax.html>
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//! or <https://doc.rust-lang.org/rust-by-example/generics.html>
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use bevy::prelude::*;
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#[derive(Debug, Clone, Eq, PartialEq, Hash)]
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enum AppState {
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MainMenu,
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InGame,
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}
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#[derive(Component)]
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struct TextToPrint(String);
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#[derive(Component, Deref, DerefMut)]
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struct PrinterTick(Timer);
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#[derive(Component)]
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struct MenuClose;
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#[derive(Component)]
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struct LevelUnload;
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fn main() {
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App::new()
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.add_plugins(DefaultPlugins)
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.add_state(AppState::MainMenu)
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.add_startup_system(setup_system)
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.add_system(print_text_system)
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.add_system_set(
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SystemSet::on_update(AppState::MainMenu).with_system(transition_to_in_game_system),
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)
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// add the cleanup systems
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.add_system_set(
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// Pass in the types your system should operate on using the ::<T> (turbofish) syntax
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SystemSet::on_exit(AppState::MainMenu).with_system(cleanup_system::<MenuClose>),
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)
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.add_system_set(
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SystemSet::on_exit(AppState::InGame).with_system(cleanup_system::<LevelUnload>),
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)
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.run();
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}
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fn setup_system(mut commands: Commands) {
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commands.spawn((
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PrinterTick(Timer::from_seconds(1.0, true)),
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TextToPrint("I will print until you press space.".to_string()),
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MenuClose,
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));
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commands.spawn((
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PrinterTick(Timer::from_seconds(1.0, true)),
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TextToPrint("I will always print".to_string()),
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LevelUnload,
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));
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}
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fn print_text_system(time: Res<Time>, mut query: Query<(&mut PrinterTick, &TextToPrint)>) {
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for (mut timer, text) in &mut query {
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if timer.tick(time.delta()).just_finished() {
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info!("{}", text.0);
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}
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}
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}
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fn transition_to_in_game_system(
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mut state: ResMut<State<AppState>>,
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keyboard_input: Res<Input<KeyCode>>,
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) {
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if keyboard_input.pressed(KeyCode::Space) {
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state.set(AppState::InGame).unwrap();
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}
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}
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// Type arguments on functions come after the function name, but before ordinary arguments.
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// Here, the `Component` trait is a trait bound on T, our generic type
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fn cleanup_system<T: Component>(mut commands: Commands, query: Query<Entity, With<T>>) {
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for e in &query {
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commands.entity(e).despawn_recursive();
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}
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}
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