forked from bevyengine/bevy
-
Notifications
You must be signed in to change notification settings - Fork 0
/
generic_system.rs
91 lines (79 loc) · 3.06 KB
/
generic_system.rs
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
//! Generic types allow us to reuse logic across many related systems,
//! allowing us to specialize our function's behavior based on which type (or types) are passed in.
//!
//! This is commonly useful for working on related components or resources,
//! where we want to have unique types for querying purposes but want them all to work the same way.
//! This is particularly powerful when combined with user-defined traits to add more functionality to these related types.
//! Remember to insert a specialized copy of the system into the schedule for each type that you want to operate on!
//!
//! For more advice on working with generic types in Rust, check out <https://doc.rust-lang.org/book/ch10-01-syntax.html>
//! or <https://doc.rust-lang.org/rust-by-example/generics.html>
use bevy::{ecs::component::Component, prelude::*};
#[derive(Debug, Clone, Eq, PartialEq, Hash)]
enum AppState {
MainMenu,
InGame,
}
#[derive(Component)]
struct TextToPrint(String);
#[derive(Component, Deref, DerefMut)]
struct PrinterTick(bevy::prelude::Timer);
#[derive(Component)]
struct MenuClose;
#[derive(Component)]
struct LevelUnload;
fn main() {
App::new()
.add_plugins(DefaultPlugins)
.add_state(AppState::MainMenu)
.add_startup_system(setup_system)
.add_system(print_text_system)
.add_system_set(
SystemSet::on_update(AppState::MainMenu).with_system(transition_to_in_game_system),
)
// add the cleanup systems
.add_system_set(
// Pass in the types your system should operate on using the ::<T> (turbofish) syntax
SystemSet::on_exit(AppState::MainMenu).with_system(cleanup_system::<MenuClose>),
)
.add_system_set(
SystemSet::on_exit(AppState::InGame).with_system(cleanup_system::<LevelUnload>),
)
.run();
}
fn setup_system(mut commands: Commands) {
commands
.spawn()
.insert(PrinterTick(bevy::prelude::Timer::from_seconds(1.0, true)))
.insert(TextToPrint(
"I will print until you press space.".to_string(),
))
.insert(MenuClose);
commands
.spawn()
.insert(PrinterTick(bevy::prelude::Timer::from_seconds(1.0, true)))
.insert(TextToPrint("I will always print".to_string()))
.insert(LevelUnload);
}
fn print_text_system(time: Res<Time>, mut query: Query<(&mut PrinterTick, &TextToPrint)>) {
for (mut timer, text) in &mut query {
if timer.tick(time.delta()).just_finished() {
info!("{}", text.0);
}
}
}
fn transition_to_in_game_system(
mut state: ResMut<State<AppState>>,
keyboard_input: Res<Input<KeyCode>>,
) {
if keyboard_input.pressed(KeyCode::Space) {
state.set(AppState::InGame).unwrap();
}
}
// Type arguments on functions come after the function name, but before ordinary arguments.
// Here, the `Component` trait is a trait bound on T, our generic type
fn cleanup_system<T: Component>(mut commands: Commands, query: Query<Entity, With<T>>) {
for e in &query {
commands.entity(e).despawn_recursive();
}
}