pub struct Sender<T> { /* private fields */ }
Expand description
Sending-half of the broadcast
channel.
May be used from many threads. Messages can be sent with
send
.
Examples
use tokio::sync::broadcast;
#[tokio::main]
async fn main() {
let (tx, mut rx1) = broadcast::channel(16);
let mut rx2 = tx.subscribe();
tokio::spawn(async move {
assert_eq!(rx1.recv().await.unwrap(), 10);
assert_eq!(rx1.recv().await.unwrap(), 20);
});
tokio::spawn(async move {
assert_eq!(rx2.recv().await.unwrap(), 10);
assert_eq!(rx2.recv().await.unwrap(), 20);
});
tx.send(10).unwrap();
tx.send(20).unwrap();
}
Implementations§
source§impl<T> Sender<T>
impl<T> Sender<T>
sourcepub fn send(&self, value: T) -> Result<usize, SendError<T>>
pub fn send(&self, value: T) -> Result<usize, SendError<T>>
Attempts to send a value to all active Receiver
handles, returning
it back if it could not be sent.
A successful send occurs when there is at least one active Receiver
handle. An unsuccessful send would be one where all associated
Receiver
handles have already been dropped.
Return
On success, the number of subscribed Receiver
handles is returned.
This does not mean that this number of receivers will see the message as
a receiver may drop before receiving the message.
Note
A return value of Ok
does not mean that the sent value will be
observed by all or any of the active Receiver
handles. Receiver
handles may be dropped before receiving the sent message.
A return value of Err
does not mean that future calls to send
will fail. New Receiver
handles may be created by calling
subscribe
.
Examples
use tokio::sync::broadcast;
#[tokio::main]
async fn main() {
let (tx, mut rx1) = broadcast::channel(16);
let mut rx2 = tx.subscribe();
tokio::spawn(async move {
assert_eq!(rx1.recv().await.unwrap(), 10);
assert_eq!(rx1.recv().await.unwrap(), 20);
});
tokio::spawn(async move {
assert_eq!(rx2.recv().await.unwrap(), 10);
assert_eq!(rx2.recv().await.unwrap(), 20);
});
tx.send(10).unwrap();
tx.send(20).unwrap();
}
sourcepub fn subscribe(&self) -> Receiver<T>
pub fn subscribe(&self) -> Receiver<T>
Creates a new Receiver
handle that will receive values sent after
this call to subscribe
.
Examples
use tokio::sync::broadcast;
#[tokio::main]
async fn main() {
let (tx, _rx) = broadcast::channel(16);
// Will not be seen
tx.send(10).unwrap();
let mut rx = tx.subscribe();
tx.send(20).unwrap();
let value = rx.recv().await.unwrap();
assert_eq!(20, value);
}
sourcepub fn len(&self) -> usize
pub fn len(&self) -> usize
Returns the number of queued values.
A value is queued until it has either been seen by all receivers that were alive at the time it was sent, or has been evicted from the queue by subsequent sends that exceeded the queue’s capacity.
Note
In contrast to Receiver::len
, this method only reports queued values and not values that
have been evicted from the queue before being seen by all receivers.
Examples
use tokio::sync::broadcast;
#[tokio::main]
async fn main() {
let (tx, mut rx1) = broadcast::channel(16);
let mut rx2 = tx.subscribe();
tx.send(10).unwrap();
tx.send(20).unwrap();
tx.send(30).unwrap();
assert_eq!(tx.len(), 3);
rx1.recv().await.unwrap();
// The len is still 3 since rx2 hasn't seen the first value yet.
assert_eq!(tx.len(), 3);
rx2.recv().await.unwrap();
assert_eq!(tx.len(), 2);
}
sourcepub fn is_empty(&self) -> bool
pub fn is_empty(&self) -> bool
Returns true if there are no queued values.
Examples
use tokio::sync::broadcast;
#[tokio::main]
async fn main() {
let (tx, mut rx1) = broadcast::channel(16);
let mut rx2 = tx.subscribe();
assert!(tx.is_empty());
tx.send(10).unwrap();
assert!(!tx.is_empty());
rx1.recv().await.unwrap();
// The queue is still not empty since rx2 hasn't seen the value.
assert!(!tx.is_empty());
rx2.recv().await.unwrap();
assert!(tx.is_empty());
}
sourcepub fn receiver_count(&self) -> usize
pub fn receiver_count(&self) -> usize
Returns the number of active receivers
An active receiver is a Receiver
handle returned from channel
or
subscribe
. These are the handles that will receive values sent on
this Sender
.
Note
It is not guaranteed that a sent message will reach this number of
receivers. Active receivers may never call recv
again before
dropping.
Examples
use tokio::sync::broadcast;
#[tokio::main]
async fn main() {
let (tx, _rx1) = broadcast::channel(16);
assert_eq!(1, tx.receiver_count());
let mut _rx2 = tx.subscribe();
assert_eq!(2, tx.receiver_count());
tx.send(10).unwrap();
}
sourcepub fn same_channel(&self, other: &Self) -> bool
pub fn same_channel(&self, other: &Self) -> bool
Returns true
if senders belong to the same channel.
Examples
use tokio::sync::broadcast;
#[tokio::main]
async fn main() {
let (tx, _rx) = broadcast::channel::<()>(16);
let tx2 = tx.clone();
assert!(tx.same_channel(&tx2));
let (tx3, _rx3) = broadcast::channel::<()>(16);
assert!(!tx3.same_channel(&tx2));
}