Threads

Rust threads work similarly to threads in other languages:

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

fn main() {
    thread::spawn(|| {
        for i in 1..10 {
            println!("Count in thread: {i}!");
            thread::sleep(Duration::from_millis(5));
        }
    });

    for i in 1..5 {
        println!("Main thread: {i}");
        thread::sleep(Duration::from_millis(5));
    }
}
  • Threads are all daemon threads, the main thread does not wait for them.
  • Thread panics are independent of each other.
    • Panics can carry a payload, which can be unpacked with downcast_ref.

Key points:

  • Notice that the thread is stopped before it reaches 10 — the main thread is not waiting.

  • Use let handle = thread::spawn(...) and later handle.join() to wait for the thread to finish.

  • Trigger a panic in the thread, notice how this doesn’t affect main.

  • Use the Result return value from handle.join() to get access to the panic payload. This is a good time to talk about Any.