Struct tokio::sync::mpsc::WeakSender

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pub struct WeakSender<T> { /* private fields */ }
Available on crate feature sync only.
Expand description

A sender that does not prevent the channel from being closed.

If all Sender instances of a channel were dropped and only WeakSender instances remain, the channel is closed.

In order to send messages, the WeakSender needs to be upgraded using WeakSender::upgrade, which returns Option<Sender>. It returns None if all Senders have been dropped, and otherwise it returns a Sender.

#Examples

use tokio::sync::mpsc::channel;

#[tokio::main]
async fn main() {
    let (tx, _rx) = channel::<i32>(15);
    let tx_weak = tx.downgrade();
   
    // Upgrading will succeed because `tx` still exists.
    assert!(tx_weak.upgrade().is_some());
   
    // If we drop `tx`, then it will fail.
    drop(tx);
    assert!(tx_weak.clone().upgrade().is_none());
}

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impl<T> WeakSender<T>

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pub fn upgrade(&self) -> Option<Sender<T>>

Tries to convert a WeakSender into a Sender. This will return Some if there are other Sender instances alive and the channel wasn’t previously dropped, otherwise None is returned.

Trait Implementations§

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impl<T> Clone for WeakSender<T>

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fn clone(&self) -> Self

Returns a copy 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 WeakSender<T>

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

Formats the value using the given formatter. Read more

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impl<T> !RefUnwindSafe for WeakSender<T>

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impl<T> Send for WeakSender<T>where T: Send,

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impl<T> Sync for WeakSender<T>where T: Send,

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impl<T> Unpin for WeakSender<T>

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impl<T> !UnwindSafe for WeakSender<T>

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impl<T> Any for Twhere 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 Twhere 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 Twhere 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> From<T> for T

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fn from(t: T) -> T

Returns the argument unchanged.

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impl<T> Instrument for T

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fn instrument(self, span: Span) -> Instrumented<Self>

Instruments this type with the provided Span, returning an Instrumented wrapper. Read more
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fn in_current_span(self) -> Instrumented<Self>

Instruments this type with the current Span, returning an Instrumented wrapper. Read more
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impl<T, U> Into<U> for Twhere 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 Twhere 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 Twhere 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 Twhere 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.
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impl<T> WithSubscriber for T

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fn with_subscriber<S>(self, subscriber: S) -> WithDispatch<Self> where S: Into<Dispatch>,

Attaches the provided Subscriber to this type, returning a WithDispatch wrapper. Read more
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fn with_current_subscriber(self) -> WithDispatch<Self>

Attaches the current default Subscriber to this type, returning a WithDispatch wrapper. Read more