main.rs

use std::thread;
use std::time::Duration;

use bevy::app::App;
use bevy::prelude::*;
use rand::Rng;

#[derive(Resource, Default)]
struct MyRes;

fn first() {
    println!("first");
}

fn random_delay1() {
    thread::sleep(Duration::from_millis(rand::thread_rng().gen_range(0..10)))
}

fn random_delay2() {
    thread::sleep(Duration::from_millis(rand::thread_rng().gen_range(0..10)))
}

fn system1(_my_res: ResMut<MyRes>) {
    println!("system1");
}

fn system2(_my_res: ResMut<MyRes>) {
    println!("system2");
}

fn main() {
    App::new()
        .add_plugins(DefaultPlugins)
        .init_resource::<MyRes>()
        .add_systems(
            Update,
            (
                first,
                random_delay1.after(first),
                system1.after(random_delay1),
                random_delay2.after(first),
                system2.after(random_delay2),
            ),
        )
        .run();
}