external_source_external_thread/
external_source_external_thread.rs

1//! How to use an external thread to run an infinite task and communicate with a channel.
2
3use bevy::prelude::*;
4// Using crossbeam_channel instead of std as std `Receiver` is `!Sync`
5use crossbeam_channel::{bounded, Receiver};
6use rand::{Rng, SeedableRng};
7use rand_chacha::ChaCha8Rng;
8
9fn main() {
10    App::new()
11        .add_event::<StreamEvent>()
12        .add_plugins(DefaultPlugins)
13        .add_systems(Startup, setup)
14        .add_systems(Update, (spawn_text, move_text))
15        .add_systems(FixedUpdate, read_stream)
16        .insert_resource(Time::<Fixed>::from_seconds(0.5))
17        .run();
18}
19
20#[derive(Resource, Deref)]
21struct StreamReceiver(Receiver<u32>);
22
23#[derive(Event)]
24struct StreamEvent(u32);
25
26fn setup(mut commands: Commands) {
27    commands.spawn(Camera2d);
28
29    let (tx, rx) = bounded::<u32>(1);
30    std::thread::spawn(move || {
31        // We're seeding the PRNG here to make this example deterministic for testing purposes.
32        // This isn't strictly required in practical use unless you need your app to be deterministic.
33        let mut rng = ChaCha8Rng::seed_from_u64(19878367467713);
34        loop {
35            // Everything here happens in another thread
36            // This is where you could connect to an external data source
37
38            // This will block until the previous value has been read in system `read_stream`
39            tx.send(rng.gen_range(0..2000)).unwrap();
40        }
41    });
42
43    commands.insert_resource(StreamReceiver(rx));
44}
45
46// This system reads from the receiver and sends events to Bevy
47fn read_stream(receiver: Res<StreamReceiver>, mut events: EventWriter<StreamEvent>) {
48    for from_stream in receiver.try_iter() {
49        events.write(StreamEvent(from_stream));
50    }
51}
52
53fn spawn_text(mut commands: Commands, mut reader: EventReader<StreamEvent>) {
54    for (per_frame, event) in reader.read().enumerate() {
55        commands.spawn((
56            Text2d::new(event.0.to_string()),
57            TextLayout::new_with_justify(JustifyText::Center),
58            Transform::from_xyz(per_frame as f32 * 100.0, 300.0, 0.0),
59        ));
60    }
61}
62
63fn move_text(
64    mut commands: Commands,
65    mut texts: Query<(Entity, &mut Transform), With<Text2d>>,
66    time: Res<Time>,
67) {
68    for (entity, mut position) in &mut texts {
69        position.translation -= Vec3::new(0.0, 100.0 * time.delta_secs(), 0.0);
70        if position.translation.y < -300.0 {
71            commands.entity(entity).despawn();
72        }
73    }
74}
external_source_external_thread/external_source_external_thread.rs

external_source_external_thread/
external_source_external_thread.rs
