[−][src]Crate async_watch
A single-producer, multi-consumer channel that only retains the last sent value.
Extracted from Tokio's tokio::sync::watch
implementation, which was written by Carl Lerche.
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. The latest value stored in the channel is accessed with
Receiver::borrow()
. Awaiting Receiver::changed()
waits for a new
value to sent by the Sender
half. Awaiting Receiver::recv()
combines
Receiver::changed()
and Receiver::borrow()
where the borrowed value
is cloned and returned.
Examples
let (tx, mut rx) = async_watch::channel("hello"); let mut rx2 = rx.clone(); // First variant executor.spawn(async move { while let Ok(value) = rx.recv().await { println!("received = {:?}", value); } }); // Second variant executor.spawn(async move { while rx2.changed().await.is_ok() { println!("received = {:?}", *rx2.borrow()); } }); tx.send("world").unwrap();
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. |