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https://github.com/bevyengine/bevy
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f16768d868
# Objective A common pattern in Rust is the [newtype](https://doc.rust-lang.org/rust-by-example/generics/new_types.html). This is an especially useful pattern in Bevy as it allows us to give common/foreign types different semantics (such as allowing it to implement `Component` or `FromWorld`) or to simply treat them as a "new type" (clever). For example, it allows us to wrap a common `Vec<String>` and do things like: ```rust #[derive(Component)] struct Items(Vec<String>); fn give_sword(query: Query<&mut Items>) { query.single_mut().0.push(String::from("Flaming Poisoning Raging Sword of Doom")); } ``` > We could then define another struct that wraps `Vec<String>` without anything clashing in the query. However, one of the worst parts of this pattern is the ugly `.0` we have to write in order to access the type we actually care about. This is why people often implement `Deref` and `DerefMut` in order to get around this. Since it's such a common pattern, especially for Bevy, it makes sense to add a derive macro to automatically add those implementations. ## Solution Added a derive macro for `Deref` and another for `DerefMut` (both exported into the prelude). This works on all structs (including tuple structs) as long as they only contain a single field: ```rust #[derive(Deref)] struct Foo(String); #[derive(Deref, DerefMut)] struct Bar { name: String, } ``` This allows us to then remove that pesky `.0`: ```rust #[derive(Component, Deref, DerefMut)] struct Items(Vec<String>); fn give_sword(query: Query<&mut Items>) { query.single_mut().push(String::from("Flaming Poisoning Raging Sword of Doom")); } ``` ### Alternatives There are other alternatives to this such as by using the [`derive_more`](https://crates.io/crates/derive_more) crate. However, it doesn't seem like we need an entire crate just yet since we only need `Deref` and `DerefMut` (for now). ### Considerations One thing to consider is that the Rust std library recommends _not_ using `Deref` and `DerefMut` for things like this: "`Deref` should only be implemented for smart pointers to avoid confusion" ([reference](https://doc.rust-lang.org/std/ops/trait.Deref.html)). Personally, I believe it makes sense to use it in the way described above, but others may disagree. ### Additional Context Discord: https://discord.com/channels/691052431525675048/692572690833473578/956648422163746827 (controversiality discussed [here](https://discord.com/channels/691052431525675048/692572690833473578/956711911481835630)) --- ## Changelog - Add `Deref` derive macro (exported to prelude) - Add `DerefMut` derive macro (exported to prelude) - Updated most newtypes in examples to use one or both derives Co-authored-by: MrGVSV <49806985+MrGVSV@users.noreply.github.com>
93 lines
2.8 KiB
Rust
93 lines
2.8 KiB
Rust
use bevy::{
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diagnostic::{FrameTimeDiagnosticsPlugin, LogDiagnosticsPlugin},
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math::Quat,
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prelude::*,
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render::camera::Camera,
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};
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use rand::Rng;
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const CAMERA_SPEED: f32 = 1000.0;
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/// This example is for performance testing purposes.
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/// See <https://github.com/bevyengine/bevy/pull/1492>
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fn main() {
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App::new()
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.add_plugin(LogDiagnosticsPlugin::default())
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.add_plugin(FrameTimeDiagnosticsPlugin::default())
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.add_plugins(DefaultPlugins)
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.add_startup_system(setup)
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.add_system(print_sprite_count.label("Tick"))
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.add_system(move_camera.after("Tick"))
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.run();
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}
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fn setup(mut commands: Commands, assets: Res<AssetServer>) {
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let mut rng = rand::thread_rng();
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let tile_size = Vec2::splat(64.0);
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let map_size = Vec2::splat(320.0);
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let half_x = (map_size.x / 2.0) as i32;
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let half_y = (map_size.y / 2.0) as i32;
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let sprite_handle = assets.load("branding/icon.png");
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// Spawns the camera
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commands
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.spawn()
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.insert_bundle(OrthographicCameraBundle::new_2d())
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.insert(Transform::from_xyz(0.0, 0.0, 1000.0));
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// Builds and spawns the sprites
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let mut sprites = vec![];
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for y in -half_y..half_y {
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for x in -half_x..half_x {
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let position = Vec2::new(x as f32, y as f32);
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let translation = (position * tile_size).extend(rng.gen::<f32>());
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let rotation = Quat::from_rotation_z(rng.gen::<f32>());
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let scale = Vec3::splat(rng.gen::<f32>() * 2.0);
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sprites.push(SpriteBundle {
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texture: sprite_handle.clone(),
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transform: Transform {
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translation,
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rotation,
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scale,
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},
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sprite: Sprite {
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custom_size: Some(tile_size),
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..default()
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},
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..default()
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});
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}
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}
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commands.spawn_batch(sprites);
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}
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// System for rotating and translating the camera
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fn move_camera(time: Res<Time>, mut camera_query: Query<&mut Transform, With<Camera>>) {
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let mut camera_transform = camera_query.single_mut();
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camera_transform.rotate(Quat::from_rotation_z(time.delta_seconds() * 0.5));
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*camera_transform = *camera_transform
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* Transform::from_translation(Vec3::X * CAMERA_SPEED * time.delta_seconds());
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}
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#[derive(Deref, DerefMut)]
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struct PrintingTimer(Timer);
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impl Default for PrintingTimer {
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fn default() -> Self {
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Self(Timer::from_seconds(1.0, true))
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}
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}
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// System for printing the number of sprites on every tick of the timer
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fn print_sprite_count(time: Res<Time>, mut timer: Local<PrintingTimer>, sprites: Query<&Sprite>) {
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timer.tick(time.delta());
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if timer.just_finished() {
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info!("Sprites: {}", sprites.iter().count(),);
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}
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}
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