[−][src]Module tokio_sync::watch
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::poll
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::poll
and Receiver::poll_ref
will always yield
the latest value.
Examples
extern crate tokio; use tokio::prelude::*; use tokio::sync::watch; let (mut tx, rx) = watch::channel("hello"); tokio::spawn(rx.for_each(|value| { println!("received = {:?}", value); Ok(()) }).map_err(|_| ())); tx.broadcast("world").unwrap();
Closing
Sender::poll_close
allows the producer to detect when all Sender
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 | Create a new watch channel, returning the "send" and "receive" handles. |