68 lines
2.0 KiB
Rust
68 lines
2.0 KiB
Rust
use bevy::prelude::*;
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/// Illustrates the different ways you can declare systems
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fn main() {
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App::build()
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.add_default_plugins()
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.add_event::<MyEvent>()
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.add_startup_system(setup)
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.add_system_init(built_system)
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.add_system(simple_system.system())
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.add_system(closure_system())
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.run();
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}
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struct MyEvent(usize);
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// resources
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struct A(usize);
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// components
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struct X(usize);
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struct Y(usize);
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// add our resources and entities
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fn setup(world: &mut World, resources: &mut Resources) {
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resources.insert(A(0));
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world.insert((), vec![(X(0), Y(1)), (X(2), Y(3))]);
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}
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// runs once for each entity with the X and Y component
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fn simple_system(x: Ref<X>, mut y: RefMut<Y>) {
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y.0 += 1;
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println!("processed entity: {} {}", x.0, y.0);
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}
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// does the same thing as the first system, but also captures the "counter" variable and uses it as internal state
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fn closure_system() -> Box<dyn Schedulable> {
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let mut counter = 0;
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(move |x: Ref<X>, mut y: RefMut<Y>| {
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y.0 += 1;
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println!("processed entity: {} {}", x.0, y.0);
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println!("ran {} times", counter);
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counter += 1;
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})
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.system()
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}
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// if you need more flexibility, you can define complex systems using the system builder
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fn built_system(resources: &mut Resources) -> Box<dyn Schedulable> {
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let mut my_event_reader = resources.get_event_reader::<MyEvent>();
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SystemBuilder::new("example")
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.read_resource::<Events<MyEvent>>()
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.write_resource::<A>()
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.with_query(<(Read<X>, Write<Y>)>::query())
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.build(
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move |_command_buffer, world, (my_events, ref mut a), query| {
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for event in my_event_reader.iter(&my_events) {
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a.0 += event.0;
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println!("modified resource A with event: {}", event.0);
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}
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for (x, mut y) in query.iter_mut(world) {
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y.0 += 1;
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println!("processed entity: {} {}", x.0, y.0);
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}
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},
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)
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}
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