Struct async_std::channel::Receiver

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

The receiving side of a channel.

Receivers can be cloned and shared among threads. When all receivers associated with a channel are dropped, the channel becomes closed.

The channel can also be closed manually by calling Receiver::close().

Receivers implement the Stream trait.

Implementations

impl<T> Receiver<T>

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

Attempts to receive a message from the channel.

If the channel is empty, or empty and closed, this method returns an error.

Examples

use async_channel::{unbounded, TryRecvError};

let (s, r) = unbounded();
assert_eq!(s.send(1).await, Ok(()));

assert_eq!(r.try_recv(), Ok(1));
assert_eq!(r.try_recv(), Err(TryRecvError::Empty));

drop(s);
assert_eq!(r.try_recv(), Err(TryRecvError::Closed));

pub fn recv(&self) -> Recv<'_, T>

Receives a message from the channel.

If the channel is empty, this method waits until there is a message.

If the channel is closed, this method receives a message or returns an error if there are no more messages.

Examples

use async_channel::{unbounded, RecvError};

let (s, r) = unbounded();

assert_eq!(s.send(1).await, Ok(()));
drop(s);

assert_eq!(r.recv().await, Ok(1));
assert_eq!(r.recv().await, Err(RecvError));

pub fn recv_blocking(&self) -> Result<T, RecvError>

Receives a message from the channel using the blocking strategy.

If the channel is empty, this method waits until there is a message. If the channel is closed, this method receives a message or returns an error if there are no more messages.

Blocking

Rather than using asynchronous waiting, like the recv method, this method will block the current thread until the message is sent.

This method should not be used in an asynchronous context. It is intended to be used such that a channel can be used in both asynchronous and synchronous contexts. Calling this method in an asynchronous context may result in deadlocks.

Examples

use async_channel::{unbounded, RecvError};

let (s, r) = unbounded();

assert_eq!(s.send_blocking(1), Ok(()));
drop(s);

assert_eq!(r.recv_blocking(), Ok(1));
assert_eq!(r.recv_blocking(), Err(RecvError));

pub fn close(&self) -> bool

Closes the channel.

Returns true if this call has closed the channel and it was not closed already.

The remaining messages can still be received.

Examples

use async_channel::{unbounded, RecvError};

let (s, r) = unbounded();
assert_eq!(s.send(1).await, Ok(()));

assert!(r.close());
assert_eq!(r.recv().await, Ok(1));
assert_eq!(r.recv().await, Err(RecvError));

pub fn is_closed(&self) -> bool

Returns true if the channel is closed.

Examples

use async_channel::{unbounded, RecvError};

let (s, r) = unbounded::<()>();
assert!(!r.is_closed());

drop(s);
assert!(r.is_closed());

pub fn is_empty(&self) -> bool

Returns true if the channel is empty.

Examples

use async_channel::unbounded;

let (s, r) = unbounded();

assert!(s.is_empty());
s.send(1).await;
assert!(!s.is_empty());

pub fn is_full(&self) -> bool

Returns true if the channel is full.

Unbounded channels are never full.

Examples

use async_channel::bounded;

let (s, r) = bounded(1);

assert!(!r.is_full());
s.send(1).await;
assert!(r.is_full());

pub fn len(&self) -> usize

Returns the number of messages in the channel.

Examples

use async_channel::unbounded;

let (s, r) = unbounded();
assert_eq!(r.len(), 0);

s.send(1).await;
s.send(2).await;
assert_eq!(r.len(), 2);

pub fn capacity(&self) -> Option<usize>

Returns the channel capacity if it’s bounded.

Examples

use async_channel::{bounded, unbounded};

let (s, r) = bounded::<i32>(5);
assert_eq!(r.capacity(), Some(5));

let (s, r) = unbounded::<i32>();
assert_eq!(r.capacity(), None);

pub fn receiver_count(&self) -> usize

Returns the number of receivers for the channel.

Examples

use async_channel::unbounded;

let (s, r) = unbounded::<()>();
assert_eq!(r.receiver_count(), 1);

let r2 = r.clone();
assert_eq!(r.receiver_count(), 2);

pub fn sender_count(&self) -> usize

Returns the number of senders for the channel.

Examples

use async_channel::unbounded;

let (s, r) = unbounded::<()>();
assert_eq!(r.sender_count(), 1);

let s2 = s.clone();
assert_eq!(r.sender_count(), 2);

pub fn downgrade(&self) -> WeakReceiver<T>

Downgrade the receiver to a weak reference.

Trait Implementations

impl<T> Clone for Receiver<T>

fn clone(&self) -> Receiver<T>

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<T> Debug for Receiver<T>

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl<T> Drop for Receiver<T>

fn drop(&mut self)

Executes the destructor for this type.

impl<T> FusedStream for Receiver<T>

fn is_terminated(&self) -> bool

Returns true if the stream should no longer be polled.

impl<T> Stream for Receiver<T>

type Item = T

Values yielded by the stream.

fn poll_next( self: Pin<&mut Receiver<T>>, cx: &mut Context<'_> ) -> Poll<Option<<Receiver<T> as Stream>::Item>>

Attempt to pull out the next value of this stream, registering the current task for wakeup if the value is not yet available, and returning None if the stream is exhausted.

fn size_hint(&self) -> (usize, Option<usize>)

Returns the bounds on the remaining length of the stream.