Module tokio::sync::watch [−][src]
A single-producer, multi-consumer channel that only retains the last sent value.
This channel is useful for watching for changes to a value from multiple points in the code base, for example, changes to configuration values.
Usage
channel
returns a Sender
/ Receiver
pair. These are
the producer and sender halves of the channel. The channel is
created with an initial value. Receiver::recv
will always
be ready upon creation and will yield either this initial value or
the latest value that has been sent by Sender
.
Calls to Receiver::recv
will always yield the latest value.
Examples
use tokio::sync::watch; let (tx, mut rx) = watch::channel("hello"); tokio::spawn(async move { while let Some(value) = rx.recv().await { println!("received = {:?}", value); } }); tx.broadcast("world")?;
Closing
Sender::closed
allows the producer to detect when all Receiver
handles have been dropped. This indicates that there is no further interest
in the values being produced and work can be stopped.
Thread safety
Both Sender
and Receiver
are thread safe. They can be moved to other
threads and can be used in a concurrent environment. Clones of Receiver
handles may be moved to separate threads and also used concurrently.
Modules
error | Watch error types |
Structs
Receiver | Receives values from the associated |
Ref | Returns a reference to the inner value |
Sender | Sends values to the associated |
Functions
channel | Creates a new watch channel, returning the “send” and “receive” handles. |