Struct tokio::sync::watch::Receiver[][src]

pub struct Receiver<T> { /* fields omitted */ }
This is supported on crate feature sync only.
Expand description

Receives values from the associated Sender.

Instances are created by the channel function.

To turn this receiver into a Stream, you can use the WatchStream wrapper.

Implementations

Returns a reference to the most recently sent value.

This method does not mark the returned value as seen, so future calls to changed may return immediately even if you have already seen the value with a call to borrow.

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");

Returns a reference to the most recently sent value and mark that value as seen.

This method marks the value as seen, so changed will not return immediately if the newest value is one previously returned by borrow_and_update.

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.

Waits for a change notification, then marks the newest value as seen.

If the newest value in the channel has not yet been marked seen when this method is called, the method marks that value seen and returns immediately. If the newest value has already been marked seen, then the method sleeps until a new message is sent by the Sender connected to this Receiver, or until the Sender is dropped.

This method returns an error if and only if the Sender is dropped.

Cancel safety

This method is cancel safe. If you use it as the event in a tokio::select! statement and some other branch completes first, then it is guaranteed that no values have been marked seen by this call to changed.

Examples
use tokio::sync::watch;

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

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

    assert!(rx.changed().await.is_ok());
    assert_eq!(*rx.borrow(), "goodbye");

    // The `tx` handle has been dropped
    assert!(rx.changed().await.is_err());
}

Trait Implementations

Returns a copy of the value. Read more

Performs copy-assignment from source. Read more

Formats the value using the given formatter. Read more

Executes the destructor for this type. Read more

Auto Trait Implementations

Blanket Implementations

Gets the TypeId of self. Read more

Immutably borrows from an owned value. Read more

Mutably borrows from an owned value. Read more

Performs the conversion.

Performs the conversion.

The resulting type after obtaining ownership.

Creates owned data from borrowed data, usually by cloning. Read more

🔬 This is a nightly-only experimental API. (toowned_clone_into)

recently added

Uses borrowed data to replace owned data, usually by cloning. Read more

The type returned in the event of a conversion error.

Performs the conversion.

The type returned in the event of a conversion error.

Performs the conversion.