Struct tokio::sync::watch::Sender

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

Sends values to the associated Receiver.

Instances are created by the channel function.

Implementations

impl<T> Sender<T>

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

Sends a new value via the channel, notifying all receivers.

pub fn borrow(&self) -> Ref<'_, T>

Returns a reference to the most recently sent value

Outstanding borrows hold a read lock. This means that long lived borrows could cause the send half to block. It is recommended to keep the borrow as short lived as possible.

Examples

use tokio::sync::watch;

let (tx, _) = watch::channel("hello");
assert_eq!(*tx.borrow(), "hello");

pub fn is_closed(&self) -> bool

Checks if the channel has been closed. This happens when all receivers have dropped.

Examples

let (tx, rx) = tokio::sync::watch::channel(());
assert!(!tx.is_closed());

drop(rx);
assert!(tx.is_closed());

pub async fn closed(&self)

Completes when all receivers have dropped.

This allows the producer to get notified when interest in the produced values is canceled and immediately stop doing work.

Cancel safety

This method is cancel safe. Once the channel is closed, it stays closed forever and all future calls to closed will return immediately.

Examples

use tokio::sync::watch;

#[tokio::main]
async fn main() {
    let (tx, rx) = watch::channel("hello");

    tokio::spawn(async move {
        // use `rx`
        drop(rx);
    });

    // Waits for `rx` to drop
    tx.closed().await;
    println!("the `rx` handles dropped")
}

pub fn receiver_count(&self) -> usize

Returns the number of receivers that currently exist

Examples

use tokio::sync::watch;

#[tokio::main]
async fn main() {
    let (tx, rx1) = watch::channel("hello");

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

    let mut _rx2 = rx1.clone();

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

Trait Implementations

impl<T: Debug> 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.