Struct std::thread::JoinHandle

pub struct JoinHandle<T>(_);

An owned permission to join on a thread (block on its termination).

A JoinHandle detaches the associated thread when it is dropped, which means that there is no longer any handle to thread and no way to join on it.

Due to platform restrictions, it is not possible to Clone this handle: the ability to join a thread is a uniquely-owned permission.

This struct is created by the thread::spawn function and the thread::Builder::spawn method.

Examples

Creation from thread::spawn:

use std::thread;

let join_handle: thread::JoinHandle<_> = thread::spawn(|| {
    // some work here
});

Creation from thread::Builder::spawn:

use std::thread;

let builder = thread::Builder::new();

let join_handle: thread::JoinHandle<_> = builder.spawn(|| {
    // some work here
}).unwrap();

Child being detached and outliving its parent:

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

let original_thread = thread::spawn(|| {
    let _detached_thread = thread::spawn(|| {
        // Here we sleep to make sure that the first thread returns before.
        thread::sleep(Duration::from_millis(10));
        // This will be called, even though the JoinHandle is dropped.
        println!("♫ Still alive ♫");
    });
});

original_thread.join().expect("The thread being joined has panicked");
println!("Original thread is joined.");

// We make sure that the new thread has time to run, before the main
// thread returns.

thread::sleep(Duration::from_millis(1000));

Methods

impl<T> JoinHandle<T>

pub fn thread(&self) -> &Thread

Extracts a handle to the underlying thread.

Examples

use std::thread;

let builder = thread::Builder::new();

let join_handle: thread::JoinHandle<_> = builder.spawn(|| {
    // some work here
}).unwrap();

let thread = join_handle.thread();
println!("thread id: {:?}", thread.id());

pub fn join(self) -> Result<T>

Waits for the associated thread to finish.

In terms of atomic memory orderings, the completion of the associated thread synchronizes with this function returning. In other words, all operations performed by that thread are ordered before all operations that happen after join returns.

If the child thread panics, Err is returned with the parameter given to panic.

Panics

This function may panic on some platforms if a thread attempts to join itself or otherwise may create a deadlock with joining threads.

Examples

use std::thread;

let builder = thread::Builder::new();

let join_handle: thread::JoinHandle<_> = builder.spawn(|| {
    // some work here
}).unwrap();
join_handle.join().expect("Couldn't join on the associated thread");

Trait Implementations

impl<T> AsRawHandle for JoinHandle<T>

fn as_raw_handle(&self) -> RawHandle

This is supported on Windows only.

Extracts the raw handle, without taking any ownership.

impl<T> IntoRawHandle for JoinHandle<T>

fn into_raw_handle(self) -> RawHandle

This is supported on Windows only.

Consumes this object, returning the raw underlying handle.

impl<T> JoinHandleExt for JoinHandle<T>

fn as_pthread_t(&self) -> RawPthread

This is supported on Unix only.

Extracts the raw pthread_t without taking ownership

fn into_pthread_t(self) -> RawPthread

This is supported on Unix only.

Consumes the thread, returning the raw pthread_t

impl<T> Debug for JoinHandle<T>

fn fmt(&self, f: &mut Formatter) -> Result

Formats the value using the given formatter.

impl<T> Send for JoinHandle<T>

impl<T> Sync for JoinHandle<T>