Threads with messages

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• We can facilitate communication between the main thread and the spawned thread.
• In this example the spawned thread is sending a message to the main thread.
• The move keyword tells Rust that the variables declared before spawning that are also used in the spawned code need to be moved. (tx in this case)
• We can use recv, which is blocking the main thread, to wait for a message from the spawned thread.
• In that case we will have to know how many messages to expect and if we are still waiting for a message while the spawned thread exits then we either get stuck or get panic!.
• Using the second loop is a better solution.

examples/threads/threads-messages/src/main.rs

use std::sync::mpsc;
use std::thread;
use std::time::Duration;

fn main() {
    let (tx, rx) = mpsc::channel();

    thread::spawn(move || {
        let val = String::from("Hello");
        tx.send(val).unwrap();

        for i in 1..=10 {
            thread::sleep(Duration::from_millis(1));
            tx.send(i.to_string()).unwrap();
        }

        //  thread::sleep(Duration::from_millis(1));
        println!("Spawned thread ends");
    });

    let received = rx.recv().unwrap();
    println!("Received: {}", received);

    // complex way for reveiving
    for _j in 1..=5 {
        let received = rx.recv().unwrap();
        println!("Received: {}", received);
    }
    println!();

    // simple code for receiving
    for received in rx {
        println!("Received: {}", received);
    }
    println!();

    println!("Main thread ends");
}

Received: Hello
Received: 1
Received: 2
Received: 3
Received: 4
Received: 5

Received: 6
Received: 7
Received: 8
Received: 9
Spawned thread ends
Received: 10

Main thread ends