rust - 从 MPSC channel 成功接收后进程永不退出

Question

代码如下:

use std::thread;
use std::sync::mpsc;

fn main() {

    //spawn threads 
    let (tx, rx) = mpsc::channel();
    for mut i in 0 .. 10 {
        let txc = tx.clone();   //clone from the main sender
        thread::spawn( move || {            
            i += 20;
            println!("Sending: {}", i);
            txc.send(i).unwrap_or_else(|e| {
                eprintln!("{}", e);
            });
        });
    }

    for received in rx {
        println!("Received: {}", received);
    }

}

代码成功运行，但挂起，进程最终没有退出。

我认为这可能与关闭 channel 端有关，我尝试通过 tx.drop() 和 rx.drop() 删除，但编译器给出了错误.

我在这里做错了什么？

Answer 1

tx在你的主线程中直到 main 结束才被丢弃功能，和rx在删除所有发件人之前不会关闭。

要解决此问题，您可以使用 <a href="https://doc.rust-lang.org/std/mem/fn.drop.html" rel="noreferrer noopener nofollow">drop</a>(tx) 手动删除它启动所有线程后:

use std::thread;
use std::sync::mpsc;

fn main() {

    //spawn threads 
    let (tx, rx) = mpsc::channel();
    for mut i in 0 .. 10 {
        let txc = tx.clone();   //clone from the main sender
        thread::spawn( move || {            
            i += 20;
            println!("Sending: {}", i);
            txc.send(i).unwrap_or_else(|e| {
                eprintln!("{}", e);
            });
        });
    }

    // drop tx manually, to ensure that only senders in spawned threads are still in use
    drop(tx);

    for received in rx {
        println!("Received: {}", received);
    }

}