Struct Sender

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

The sending side of a channel.

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

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

Implementations

impl<T> Sender<T>

pub fn try_send(&self, msg: T) -> Result<(), TrySendError<T>>

Attempts to send a message into the channel.

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

Examples

use async_channel::{bounded, TrySendError};

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

assert_eq!(s.try_send(1), Ok(()));
assert_eq!(s.try_send(2), Err(TrySendError::Full(2)));

drop(r);
assert_eq!(s.try_send(3), Err(TrySendError::Closed(3)));

pub fn send(&self, msg: T) -> Send<'_, T>

Sends a message into the channel.

If the channel is full, this method waits until there is space for a message.

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

Examples

use async_channel::{unbounded, SendError};

let (s, r) = unbounded();

assert_eq!(s.send(1).await, Ok(()));
drop(r);
assert_eq!(s.send(2).await, Err(SendError(2)));

pub fn send_blocking(&self, msg: T) -> Result<(), SendError<T>>

Sends a message into this channel using the blocking strategy.

If the channel is full, this method will block until there is room. If the channel is closed, this method returns an error.

Blocking

Rather than using asynchronous waiting, like the send 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, SendError};

let (s, r) = unbounded();

assert_eq!(s.send_blocking(1), Ok(()));
drop(r);
assert_eq!(s.send_blocking(2), Err(SendError(2)));

pub fn force_send(&self, msg: T) -> Result<Option<T>, SendError<T>>

Forcefully push a message into this channel.

If the channel is full, this method will replace an existing message in the channel and return it as Ok(Some(value)). If the channel is closed, this method will return an error.

Examples

use async_channel::{bounded, SendError};

let (s, r) = bounded(3);

assert_eq!(s.send(1).await, Ok(()));
assert_eq!(s.send(2).await, Ok(()));
assert_eq!(s.force_send(3), Ok(None));
assert_eq!(s.force_send(4), Ok(Some(1)));

assert_eq!(r.recv().await, Ok(2));
assert_eq!(r.recv().await, Ok(3));
assert_eq!(r.recv().await, Ok(4));

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!(s.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!(!s.is_closed());

drop(r);
assert!(s.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!(!s.is_full());
s.send(1).await;
assert!(s.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!(s.len(), 0);

s.send(1).await;
s.send(2).await;
assert_eq!(s.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!(s.capacity(), Some(5));

let (s, r) = unbounded::<i32>();
assert_eq!(s.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!(s.receiver_count(), 1);

let r2 = r.clone();
assert_eq!(s.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!(s.sender_count(), 1);

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

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

Downgrade the sender to a weak reference.

Trait Implementations

impl<T> Clone for Sender<T>

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

Returns a copy of the value.

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

Performs copy-assignment from source.

impl<T> Debug for Sender<T>

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

Formats the value using the given formatter.

impl<T> Drop for Sender<T>

fn drop(&mut self)

Executes the destructor for this type.