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For the release documentation, please see docs.rs, instead.

Struct tracing::dispatch::WeakDispatch

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pub struct WeakDispatch { /* private fields */ }
Expand description

WeakDispatch is a version of Dispatch that holds a non-owning reference to a collector.

The collector may be accessed by calling WeakDispatch::upgrade, which returns an Option<Dispatch>. If all Dispatch clones that point at the collector have been dropped, WeakDispatch::upgrade will return None. Otherwise, it will return Some(Dispatch).

A WeakDispatch may be created from a Dispatch by calling the Dispatch::downgrade method. The primary use for creating a WeakDispatch is to allow a collector to hold a cyclical reference to itself without creating a memory leak. See here for details.

This type is analogous to the std::sync::Weak type, but for a Dispatch rather than an Arc.

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impl WeakDispatch

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pub fn upgrade(&self) -> Option<Dispatch>

Attempts to upgrade this WeakDispatch to a Dispatch.

Returns None if the referenced Dispatch has already been dropped.

§Examples
static COLLECTOR: NoCollector = NoCollector::new();
let strong = Dispatch::new(COLLECTOR);
let weak = strong.downgrade();

// The strong here keeps it alive, so we can still access the object.
assert!(weak.upgrade().is_some());

drop(strong); // But not any more.
assert!(weak.upgrade().is_none());

Trait Implementations§

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impl Clone for WeakDispatch

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fn clone(&self) -> WeakDispatch

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 Debug for WeakDispatch

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

Formats the value using the given formatter. Read more

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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> 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 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.
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impl<T> WithCollector for T

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fn with_collector<C>(self, collector: C) -> WithDispatch<Self>
where C: Into<Dispatch>,

Available on crate feature std only.
Attaches the provided collector to this type, returning a WithDispatch wrapper. Read more
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fn with_current_collector(self) -> WithDispatch<Self>

Available on crate feature std only.
Attaches the current default collector to this type, returning a WithDispatch wrapper. Read more