SyncSender in std::sync::mpsc - Rust
Description: The sending-half of Rust’s synchronous `sync_channel` type.

## SyncSender

# Struct SyncSender

1.0.0 · Source

    pub struct SyncSender<T> { /* private fields */ }

Expand description

The sending-half of Rust’s synchronous `sync_channel` type.

Messages can be sent through this channel with `send` or `try_send`.

`send` will block if there is no space in the internal buffer.

## §Examples

    use std::sync::mpsc::sync_channel;
    use std::thread;

    // Create a sync_channel with buffer size 2
    let (sync_sender, receiver) = sync_channel(2);
    let sync_sender2 = sync_sender.clone();

    // First thread owns sync_sender
    thread::spawn(move || {
        sync_sender.send(1).unwrap();
        sync_sender.send(2).unwrap();
    });

    // Second thread owns sync_sender2
    thread::spawn(move || {
        sync_sender2.send(3).unwrap();
        // thread will now block since the buffer is full
        println!("Thread unblocked!");
    });

    let mut msg;

    msg = receiver.recv().unwrap();
    println!("message {msg} received");

    // "Thread unblocked!" will be printed now

    msg = receiver.recv().unwrap();
    println!("message {msg} received");

    msg = receiver.recv().unwrap();

    println!("message {msg} received");

## Implementations§

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### impl<T> SyncSender<T>

1.0.0 · Source

#### pub fn send(&self, t: T) -> Result<(), SendError<T>>

Sends a value on this synchronous channel.

This function will block until space in the internal buffer becomes available or a receiver is available to hand off the message to.

Note that a successful send does not guarantee that the receiver will ever see the data if there is a buffer on this channel. Items may be enqueued in the internal buffer for the receiver to receive at a later time. If the buffer size is 0, however, the channel becomes a rendezvous channel and it guarantees that the receiver has indeed received the data if this function returns success.

This function will never panic, but it may return `Err` if the `Receiver` has disconnected and is no longer able to receive information.

##### §Examples

    use std::sync::mpsc::sync_channel;
    use std::thread;

    // Create a rendezvous sync_channel with buffer size 0
    let (sync_sender, receiver) = sync_channel(0);

    thread::spawn(move || {
       println!("sending message...");
       sync_sender.send(1).unwrap();
       // Thread is now blocked until the message is received

       println!("...message received!");
    });

    let msg = receiver.recv().unwrap();
    assert_eq!(1, msg);

1.0.0 · Source

#### pub fn try_send(&self, t: T) -> Result<(), TrySendError<T>>

Attempts to send a value on this channel without blocking.

This method differs from `send` by returning immediately if the channel’s buffer is full or no receiver is waiting to acquire some data. Compared with `send`, this function has two failure cases instead of one (one for disconnection, one for a full buffer).

See `send` for notes about guarantees of whether the receiver has received the data or not if this function is successful.

##### §Examples

    use std::sync::mpsc::sync_channel;
    use std::thread;

    // Create a sync_channel with buffer size 1
    let (sync_sender, receiver) = sync_channel(1);
    let sync_sender2 = sync_sender.clone();

    // First thread owns sync_sender
    let handle1 = thread::spawn(move || {
        sync_sender.send(1).unwrap();
        sync_sender.send(2).unwrap();
        // Thread blocked
    });

    // Second thread owns sync_sender2
    let handle2 = thread::spawn(move || {
        // This will return an error and send
        // no message if the buffer is full
        let _ = sync_sender2.try_send(3);
    });

    let mut msg;
    msg = receiver.recv().unwrap();
    println!("message {msg} received");

    msg = receiver.recv().unwrap();
    println!("message {msg} received");

    // Third message may have never been sent
    match receiver.try_recv() {
        Ok(msg) => println!("message {msg} received"),
        Err(_) => println!("the third message was never sent"),
    }

    // Wait for threads to complete
    handle1.join().unwrap();
    handle2.join().unwrap();

## Trait Implementations§

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### impl<T> Clone for SyncSender<T>

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#### fn clone(&self) -> SyncSender<T>

Returns a duplicate of the value. Read more
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#### fn clone_from(&mut self, source: &Self)

Performs copy-assignment from `source`. Read more
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### impl<T> Debug for SyncSender<T>

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#### fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter. Read more
1.0.0 · Source§

### impl<T: Send> Send for SyncSender<T>

## Auto Trait Implementations§

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### impl<T> Freeze for SyncSender<T>

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### impl<T> RefUnwindSafe for SyncSender<T>

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### impl<T> Sync for SyncSender<T>
where T: Send,

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### impl<T> Unpin for SyncSender<T>

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### impl<T> UnwindSafe for SyncSender<T>

## Blanket Implementations§

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### impl<T> Any for T
where T: 'static + ?Sized,

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#### fn type_id(&self) -> TypeId

Gets the `TypeId` of `self`. Read more
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### impl<T> Borrow<T> for T
where T: ?Sized,

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#### fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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### impl<T> BorrowMut<T> for T
where T: ?Sized,

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#### fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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### impl<T> CloneToUninit for T
where T: Clone,

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#### unsafe fn clone_to_uninit(&self, dest: *mut u8)

🔬This is a nightly-only experimental API. (`clone_to_uninit` #126799)
Performs copy-assignment from `self` to `dest`. Read more
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### impl<T> From<T> for T

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#### fn from(t: T) -> T

Returns the argument unchanged.

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### impl<T, U> Into<U> for T
where U: From<T>,

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#### fn into(self) -> U

Calls `U::from(self)`.

That is, this conversion is whatever the implementation of `From<T> for U` chooses to do.

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### impl<T> ToOwned for T
where T: Clone,

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#### type Owned = T

The resulting type after obtaining ownership.
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#### fn to_owned(&self) -> T

Creates owned data from borrowed data, usually by cloning. Read more
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#### fn clone_into(&self, target: &mut T)

Uses borrowed data to replace owned data, usually by cloning. Read more
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### impl<T, U> TryFrom<U> for T
where U: Into<T>,

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#### type Error = Infallible

The type returned in the event of a conversion error.
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#### fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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### impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

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#### type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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#### fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.