W3cubDocs

/Rust

Struct std::sync::mpsc::Receiver

pub struct Receiver<T> { /* fields omitted */ }

The receiving half of Rust's channel (or sync_channel) type. This half can only be owned by one thread.

Messages sent to the channel can be retrieved using recv.

Examples

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

let (send, recv) = channel();

thread::spawn(move || {
    send.send("Hello world!").unwrap();
    thread::sleep(Duration::from_secs(2)); // block for two seconds
    send.send("Delayed for 2 seconds").unwrap();
});

println!("{}", recv.recv().unwrap()); // Received immediately
println!("Waiting...");
println!("{}", recv.recv().unwrap()); // Received after 2 seconds

Methods

impl<T> Receiver<T>[src]

pub fn try_recv(&self) -> Result<T, TryRecvError>[src]

Attempts to return a pending value on this receiver without blocking.

This method will never block the caller in order to wait for data to become available. Instead, this will always return immediately with a possible option of pending data on the channel.

This is useful for a flavor of "optimistic check" before deciding to block on a receiver.

Compared with recv, this function has two failure cases instead of one (one for disconnection, one for an empty buffer).

Examples

use std::sync::mpsc::{Receiver, channel};

let (_, receiver): (_, Receiver<i32>) = channel();

assert!(receiver.try_recv().is_err());

pub fn recv(&self) -> Result<T, RecvError>[src]

Attempts to wait for a value on this receiver, returning an error if the corresponding channel has hung up.

This function will always block the current thread if there is no data available and it's possible for more data to be sent. Once a message is sent to the corresponding Sender (or SyncSender), then this receiver will wake up and return that message.

If the corresponding Sender has disconnected, or it disconnects while this call is blocking, this call will wake up and return Err to indicate that no more messages can ever be received on this channel. However, since channels are buffered, messages sent before the disconnect will still be properly received.

Examples

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

let (send, recv) = mpsc::channel();
let handle = thread::spawn(move || {
    send.send(1u8).unwrap();
});

handle.join().unwrap();

assert_eq!(Ok(1), recv.recv());

Buffering behavior:

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

let (send, recv) = mpsc::channel();
let handle = thread::spawn(move || {
    send.send(1u8).unwrap();
    send.send(2).unwrap();
    send.send(3).unwrap();
    drop(send);
});

// wait for the thread to join so we ensure the sender is dropped
handle.join().unwrap();

assert_eq!(Ok(1), recv.recv());
assert_eq!(Ok(2), recv.recv());
assert_eq!(Ok(3), recv.recv());
assert_eq!(Err(RecvError), recv.recv());

pub fn recv_timeout(&self, timeout: Duration) -> Result<T, RecvTimeoutError>[src]1.12.0

Attempts to wait for a value on this receiver, returning an error if the corresponding channel has hung up, or if it waits more than timeout.

This function will always block the current thread if there is no data available and it's possible for more data to be sent. Once a message is sent to the corresponding Sender (or SyncSender), then this receiver will wake up and return that message.

If the corresponding Sender has disconnected, or it disconnects while this call is blocking, this call will wake up and return Err to indicate that no more messages can ever be received on this channel. However, since channels are buffered, messages sent before the disconnect will still be properly received.

Known Issues

There is currently a known issue (see #39364) that causes recv_timeout to panic unexpectedly with the following example:

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

let (tx, rx) = channel::<String>();

thread::spawn(move || {
    let d = Duration::from_millis(10);
    loop {
        println!("recv");
        let _r = rx.recv_timeout(d);
    }
});

thread::sleep(Duration::from_millis(100));
let _c1 = tx.clone();

thread::sleep(Duration::from_secs(1));

Examples

Successfully receiving value before encountering timeout:

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

let (send, recv) = mpsc::channel();

thread::spawn(move || {
    send.send('a').unwrap();
});

assert_eq!(
    recv.recv_timeout(Duration::from_millis(400)),
    Ok('a')
);

Receiving an error upon reaching timeout:

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

let (send, recv) = mpsc::channel();

thread::spawn(move || {
    thread::sleep(Duration::from_millis(800));
    send.send('a').unwrap();
});

assert_eq!(
    recv.recv_timeout(Duration::from_millis(400)),
    Err(mpsc::RecvTimeoutError::Timeout)
);

pub fn recv_deadline(&self, deadline: Instant) -> Result<T, RecvTimeoutError>[src]

ūüĒ¨ This is a nightly-only experimental API. (deadline_api #46316)

Attempts to wait for a value on this receiver, returning an error if the corresponding channel has hung up, or if deadline is reached.

This function will always block the current thread if there is no data available and it's possible for more data to be sent. Once a message is sent to the corresponding Sender (or SyncSender), then this receiver will wake up and return that message.

If the corresponding Sender has disconnected, or it disconnects while this call is blocking, this call will wake up and return Err to indicate that no more messages can ever be received on this channel. However, since channels are buffered, messages sent before the disconnect will still be properly received.

Examples

Successfully receiving value before reaching deadline:

#![feature(deadline_api)]
use std::thread;
use std::time::{Duration, Instant};
use std::sync::mpsc;

let (send, recv) = mpsc::channel();

thread::spawn(move || {
    send.send('a').unwrap();
});

assert_eq!(
    recv.recv_deadline(Instant::now() + Duration::from_millis(400)),
    Ok('a')
);

Receiving an error upon reaching deadline:

#![feature(deadline_api)]
use std::thread;
use std::time::{Duration, Instant};
use std::sync::mpsc;

let (send, recv) = mpsc::channel();

thread::spawn(move || {
    thread::sleep(Duration::from_millis(800));
    send.send('a').unwrap();
});

assert_eq!(
    recv.recv_deadline(Instant::now() + Duration::from_millis(400)),
    Err(mpsc::RecvTimeoutError::Timeout)
);

pub fn iter(&self) -> Iter<T>[src]

‚ďėImportant traits for Iter<'a, T>
impl<'a, T> Iterator for Iter<'a, T>
    type Item = T;

Returns an iterator that will block waiting for messages, but never panic!. It will return None when the channel has hung up.

Examples

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

let (send, recv) = channel();

thread::spawn(move || {
    send.send(1).unwrap();
    send.send(2).unwrap();
    send.send(3).unwrap();
});

let mut iter = recv.iter();
assert_eq!(iter.next(), Some(1));
assert_eq!(iter.next(), Some(2));
assert_eq!(iter.next(), Some(3));
assert_eq!(iter.next(), None);

pub fn try_iter(&self) -> TryIter<T>[src]1.15.0

‚ďėImportant traits for TryIter<'a, T>
impl<'a, T> Iterator for TryIter<'a, T>
    type Item = T;

Returns an iterator that will attempt to yield all pending values. It will return None if there are no more pending values or if the channel has hung up. The iterator will never panic! or block the user by waiting for values.

Examples

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

let (sender, receiver) = channel();

// nothing is in the buffer yet
assert!(receiver.try_iter().next().is_none());

thread::spawn(move || {
    thread::sleep(Duration::from_secs(1));
    sender.send(1).unwrap();
    sender.send(2).unwrap();
    sender.send(3).unwrap();
});

// nothing is in the buffer yet
assert!(receiver.try_iter().next().is_none());

// block for two seconds
thread::sleep(Duration::from_secs(2));

let mut iter = receiver.try_iter();
assert_eq!(iter.next(), Some(1));
assert_eq!(iter.next(), Some(2));
assert_eq!(iter.next(), Some(3));
assert_eq!(iter.next(), None);

Trait Implementations

impl<T> Debug for Receiver<T>[src]1.8.0

impl<T> Drop for Receiver<T>[src]

impl<T: Send> Send for Receiver<T>[src]

impl<T> !Sync for Receiver<T>[src]

impl<'a, T> IntoIterator for &'a Receiver<T>[src]1.1.0

type Item = T

The type of the elements being iterated over.

type IntoIter = Iter<'a, T>

Which kind of iterator are we turning this into?

‚ďėImportant traits for Iter<'a, T>
impl<'a, T> Iterator for Iter<'a, T>
    type Item = T;

impl<T> IntoIterator for Receiver<T>[src]1.1.0

type Item = T

The type of the elements being iterated over.

type IntoIter = IntoIter<T>

Which kind of iterator are we turning this into?

‚ďėImportant traits for IntoIter<T>
impl<T> Iterator for IntoIter<T>
    type Item = T;

Auto Trait Implementations

impl<T> !UnwindSafe for Receiver<T>

impl<T> !RefUnwindSafe for Receiver<T>

impl<T> Unpin for Receiver<T>

Blanket Implementations

impl<T, U> TryFrom<U> for T where
    U: Into<T>, 
[src]

type Error = Infallible

The type returned in the event of a conversion error.

impl<I> IntoIterator for I where
    I: Iterator, 
[src]

type Item = <I as Iterator>::Item

The type of the elements being iterated over.

type IntoIter = I

Which kind of iterator are we turning this into?

impl<T, U> Into<U> for T where
    U: From<T>, 
[src]

impl<T> From<T> for T[src]

impl<T, U> TryInto<U> for T where
    U: TryFrom<T>, 
[src]

type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.

impl<T> Borrow<T> for T where
    T: ?Sized, 
[src]

‚ďėImportant traits for &'_ mut F
impl<'_, F> Future for &'_ mut F where
    F: Unpin + Future + ?Sized, 
    type Output = <F as Future>::Output;
impl<'_, I> Iterator for &'_ mut I where
    I: Iterator + ?Sized, 
    type Item = <I as Iterator>::Item;
impl<'_, R: Read + ?Sized> Read for &'_ mut R
impl<'_, W: Write + ?Sized> Write for &'_ mut W

impl<T> BorrowMut<T> for T where
    T: ?Sized, 
[src]

‚ďėImportant traits for &'_ mut F
impl<'_, F> Future for &'_ mut F where
    F: Unpin + Future + ?Sized, 
    type Output = <F as Future>::Output;
impl<'_, I> Iterator for &'_ mut I where
    I: Iterator + ?Sized, 
    type Item = <I as Iterator>::Item;
impl<'_, R: Read + ?Sized> Read for &'_ mut R
impl<'_, W: Write + ?Sized> Write for &'_ mut W

impl<T> Any for T where
    T: 'static + ?Sized, 
[src]

© 2010 The Rust Project Developers
Licensed under the Apache License, Version 2.0 or the MIT license, at your option.
https://doc.rust-lang.org/std/sync/mpsc/struct.Receiver.html