bevy/examples/async_tasks/external_source_external_thread.rs
CatThingy 89cbc78d3d
Require #[derive(Event)] on all Events (#7086)
# Objective

Be consistent with `Resource`s and `Components` and have `Event` types
be more self-documenting.
Although not susceptible to accidentally using a function instead of a
value due to `Event`s only being initialized by their type, much of the
same reasoning for removing the blanket impl on `Resource` also applies
here.

* Not immediately obvious if a type is intended to be an event
* Prevent invisible conflicts if the same third-party or primitive types
are used as events
* Allows for further extensions (e.g. opt-in warning for missed events)

## Solution

Remove the blanket impl for the `Event` trait. Add a derive macro for
it.

---

## Changelog

- `Event` is no longer implemented for all applicable types. Add the
`#[derive(Event)]` macro for events.

## Migration Guide

* Add the `#[derive(Event)]` macro for events. Third-party types used as
events should be wrapped in a newtype.
2023-06-06 14:44:32 +00:00

83 lines
2.5 KiB
Rust

//! How to use an external thread to run an infinite task and communicate with a channel.
use bevy::prelude::*;
// Using crossbeam_channel instead of std as std `Receiver` is `!Sync`
use crossbeam_channel::{bounded, Receiver};
use rand::Rng;
use std::time::{Duration, Instant};
fn main() {
App::new()
.add_event::<StreamEvent>()
.add_plugins(DefaultPlugins)
.add_systems(Startup, setup)
.add_systems(Update, (read_stream, spawn_text, move_text))
.run();
}
#[derive(Resource, Deref)]
struct StreamReceiver(Receiver<u32>);
#[derive(Event)]
struct StreamEvent(u32);
fn setup(mut commands: Commands) {
commands.spawn(Camera2dBundle::default());
let (tx, rx) = bounded::<u32>(10);
std::thread::spawn(move || loop {
// Everything here happens in another thread
// This is where you could connect to an external data source
let mut rng = rand::thread_rng();
let start_time = Instant::now();
let duration = Duration::from_secs_f32(rng.gen_range(0.0..0.2));
while start_time.elapsed() < duration {
// Spinning for 'duration', simulating doing hard work!
}
tx.send(rng.gen_range(0..2000)).unwrap();
});
commands.insert_resource(StreamReceiver(rx));
}
// This system reads from the receiver and sends events to Bevy
fn read_stream(receiver: Res<StreamReceiver>, mut events: EventWriter<StreamEvent>) {
for from_stream in receiver.try_iter() {
events.send(StreamEvent(from_stream));
}
}
fn spawn_text(mut commands: Commands, mut reader: EventReader<StreamEvent>) {
let text_style = TextStyle {
font_size: 20.0,
color: Color::WHITE,
..default()
};
for (per_frame, event) in reader.iter().enumerate() {
commands.spawn(Text2dBundle {
text: Text::from_section(event.0.to_string(), text_style.clone())
.with_alignment(TextAlignment::Center),
transform: Transform::from_xyz(
per_frame as f32 * 100.0 + rand::thread_rng().gen_range(-40.0..40.0),
300.0,
0.0,
),
..default()
});
}
}
fn move_text(
mut commands: Commands,
mut texts: Query<(Entity, &mut Transform), With<Text>>,
time: Res<Time>,
) {
for (entity, mut position) in &mut texts {
position.translation -= Vec3::new(0.0, 100.0 * time.delta_seconds(), 0.0);
if position.translation.y < -300.0 {
commands.entity(entity).despawn();
}
}
}