c26be39719
# Objective - Since #4224, using labels which only refer to one system doesn't make sense. ## Solution - Remove some of those. ## Future work - We should remove the ability to use strings as system labels entirely. I haven't in this PR because there are tests which use this, and that's a lot of code to change. - The only use cases for labels are either intra-crate, which use #4224, or inter-crate, which should either use #4224 or explicit types. Neither of those should use strings.
64 lines
2.4 KiB
Rust
64 lines
2.4 KiB
Rust
use bevy_ecs::{event::Events, prelude::*};
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// In this example a system sends a custom event with a 50/50 chance during any frame.
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// If an event was send, it will be printed by the console in a receiving system.
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fn main() {
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// Create a new empty world and add the event as a resource
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let mut world = World::new();
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world.insert_resource(Events::<MyEvent>::default());
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// Create a schedule and a stage
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let mut schedule = Schedule::default();
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// Events need to be updated in every frame. This update should happen before we use
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// the events. To guarantee this, we can let the update run in an earlier stage than our logic.
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// Here we will use a stage called "first" that will always run it's systems before the Stage
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// called "second". In "first" we update the events and in "second" we run our systems
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// sending and receiving events.
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let mut first = SystemStage::parallel();
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first.add_system(Events::<MyEvent>::update_system);
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schedule.add_stage("first", first);
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// Add systems sending and receiving events to a "second" Stage
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let mut second = SystemStage::parallel();
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second.add_system(sending_system);
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second.add_system(receiving_system.after(sending_system));
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// Run the "second" Stage after the "first" Stage, so our Events always get updated before we use them
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schedule.add_stage_after("first", "second", second);
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// Simulate 10 frames of our world
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for iteration in 1..=10 {
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println!("Simulating frame {}/10", iteration);
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schedule.run(&mut world);
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}
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}
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// This is our event that we will send and receive in systems
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struct MyEvent {
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pub message: String,
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pub random_value: f32,
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}
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// In every frame we will send an event with a 50/50 chance
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fn sending_system(mut event_writer: EventWriter<MyEvent>) {
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let random_value: f32 = rand::random();
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if random_value > 0.5 {
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event_writer.send(MyEvent {
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message: "A random event with value > 0.5".to_string(),
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random_value,
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});
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}
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}
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// This system listens for events of the type MyEvent
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// If an event is received it will be printed to the console
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fn receiving_system(mut event_reader: EventReader<MyEvent>) {
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for my_event in event_reader.iter() {
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println!(
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" Received message {:?}, with random value of {}",
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my_event.message, my_event.random_value
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);
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}
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}
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