Struct tokio::sync::broadcast::Sender

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

Sending-half of the broadcast channel.

May be used from many threads. Messages can be sent with [send][Sender::send].

Examples

use tokio::sync::broadcast;

#[tokio::main]
async fn main() {
    let (tx, mut rx1) = broadcast::channel(16);
    let mut rx2 = tx.subscribe();

    tokio::spawn(async move {
        assert_eq!(rx1.recv().await.unwrap(), 10);
        assert_eq!(rx1.recv().await.unwrap(), 20);
    });

    tokio::spawn(async move {
        assert_eq!(rx2.recv().await.unwrap(), 10);
        assert_eq!(rx2.recv().await.unwrap(), 20);
    });

    tx.send(10).unwrap();
    tx.send(20).unwrap();
}

Implementations

impl<T> Sender<T>

pub fn send(&self, value: T) -> Result<usize, SendError<T>>

Attempts to send a value to all active Receiver handles, returning it back if it could not be sent.

A successful send occurs when there is at least one active Receiver handle. An unsuccessful send would be one where all associated Receiver handles have already been dropped.

Return

On success, the number of subscribed Receiver handles is returned. This does not mean that this number of receivers will see the message as a receiver may drop before receiving the message.

Note

A return value of Ok does not mean that the sent value will be observed by all or any of the active Receiver handles. Receiver handles may be dropped before receiving the sent message.

A return value of Err does not mean that future calls to send will fail. New Receiver handles may be created by calling subscribe.

Examples

use tokio::sync::broadcast;

#[tokio::main]
async fn main() {
    let (tx, mut rx1) = broadcast::channel(16);
    let mut rx2 = tx.subscribe();

    tokio::spawn(async move {
        assert_eq!(rx1.recv().await.unwrap(), 10);
        assert_eq!(rx1.recv().await.unwrap(), 20);
    });

    tokio::spawn(async move {
        assert_eq!(rx2.recv().await.unwrap(), 10);
        assert_eq!(rx2.recv().await.unwrap(), 20);
    });

    tx.send(10).unwrap();
    tx.send(20).unwrap();
}

pub fn subscribe(&self) -> Receiver<T>

Creates a new [Receiver] handle that will receive values sent after this call to subscribe.

Examples

use tokio::sync::broadcast;

#[tokio::main]
async fn main() {
    let (tx, _rx) = broadcast::channel(16);

    // Will not be seen
    tx.send(10).unwrap();

    let mut rx = tx.subscribe();

    tx.send(20).unwrap();

    let value = rx.recv().await.unwrap();
    assert_eq!(20, value);
}

pub fn receiver_count(&self) -> usize

Returns the number of active receivers

An active receiver is a Receiver handle returned from channel or subscribe. These are the handles that will receive values sent on this Sender.

Note

It is not guaranteed that a sent message will reach this number of receivers. Active receivers may never call recv again before dropping.

Examples

use tokio::sync::broadcast;

#[tokio::main]
async fn main() {
    let (tx, _rx1) = broadcast::channel(16);

    assert_eq!(1, tx.receiver_count());

    let mut _rx2 = tx.subscribe();

    assert_eq!(2, tx.receiver_count());

    tx.send(10).unwrap();
}

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, fmt: &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.

impl<T: Send> Send for Sender<T>

impl<T: Send> Sync for Sender<T>