Struct WeakSender

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

A sender that does not prevent the channel from being closed.

If all Sender instances of a channel were dropped and only WeakSender instances remain, the channel is closed.

In order to send messages, the WeakSender needs to be upgraded using WeakSender::upgrade, which returns Option<Sender>. It returns None if all Senders have been dropped, and otherwise it returns a Sender.

Examples

use tokio::sync::mpsc::channel;

#[tokio::main]
async fn main() {
    let (tx, _rx) = channel::<i32>(15);
    let tx_weak = tx.downgrade();

    // Upgrading will succeed because `tx` still exists.
    assert!(tx_weak.upgrade().is_some());

    // If we drop `tx`, then it will fail.
    drop(tx);
    assert!(tx_weak.clone().upgrade().is_none());
}

Implementations

impl<T> WeakSender<T>

pub fn upgrade(&self) -> Option<Sender<T>>

Tries to convert a WeakSender into a Sender. This will return Some if there are other Sender instances alive and the channel wasn’t previously dropped, otherwise None is returned.

pub fn strong_count(&self) -> usize

Returns the number of Sender handles.

pub fn weak_count(&self) -> usize

Returns the number of WeakSender handles.

Trait Implementations

impl<T> Clone for WeakSender<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 for WeakSender<T>

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

Formats the value using the given formatter.

impl<T> Drop for WeakSender<T>

fn drop(&mut self)

Executes the destructor for this type.