Struct tokio::sync::watch::Receiver

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

Receives values from the associated Sender.

Instances are created by the channel function.

Implementations

impl<T> Receiver<T>

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

impl<T: Clone> Receiver<T>

pub async fn recv(&mut self) -> Option<T>

Attempts to clone the latest value sent via the channel.

If this is the first time the function is called on a Receiver instance, then the function completes immediately with the current value held by the channel. On the next call, the function waits until a new value is sent in the channel.

None is returned if the Sender half is dropped.

Examples

use tokio::sync::watch;

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

    let v = rx.recv().await.unwrap();
    assert_eq!(v, "hello");

    tokio::spawn(async move {
        tx.broadcast("goodbye").unwrap();
    });

    // Waits for the new task to spawn and send the value.
    let v = rx.recv().await.unwrap();
    assert_eq!(v, "goodbye");

    let v = rx.recv().await;
    assert!(v.is_none());
}

Trait Implementations

impl<T> Clone for Receiver<T>

fn clone(&self) -> Self

Returns a copy of the value.

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

Performs copy-assignment from source.

impl<T: Debug> Debug for Receiver<T>

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

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: Clone> Stream for Receiver<T>

type Item = T

Values yielded by the stream.

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

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.