Struct `WeakDispatch`

pub struct WeakDispatch { /* private fields */ }

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

The Subscriber may be accessed by calling WeakDispatch::upgrade, which returns an Option<Dispatch>. If all Dispatch clones that point at the Subscriber 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 Subscriber` 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.

Implementations

`impl WeakDispatch`

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

Attempts to upgrade this WeakDispatch to a Dispatch.

Returns None if the referenced Dispatch has already been dropped.

Examples

# use tracing_core::subscriber::NoSubscriber;
# use tracing_core::dispatcher::Dispatch;
let strong = Dispatch::new(NoSubscriber::default());
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

`impl Clone for WeakDispatch`

fn clone(&self) -> WeakDispatch

`impl Debug for WeakDispatch`

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

Auto Trait Implementations

`impl !RefUnwindSafe for WeakDispatch`

`impl !UnwindSafe for WeakDispatch`

`impl Freeze for WeakDispatch`

`impl Send for WeakDispatch`

`impl Sync for WeakDispatch`

`impl Unpin for WeakDispatch`

`impl UnsafeUnpin for WeakDispatch`

Blanket Implementations

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

fn type_id(&self) -> TypeId

`impl<T> Borrow<T> for WeakDispatch where T: ?Sized,`

fn borrow(&self) -> &T

`impl<T> BorrowMut<T> for WeakDispatch where T: ?Sized,`

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

`impl<T> CloneToUninit for WeakDispatch where T: Clone,`

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

`impl<T> From<T> for WeakDispatch`

fn from(t: T) -> T: Returns the argument unchanged.

`impl<T> ToOwned for WeakDispatch where T: Clone,`

type Owned = T;
fn to_owned(&self) -> T
fn clone_into(&self, target: &mut T)

`impl<T, U> Into<U> for WeakDispatch where U: From<T>,`

fn into(self) -> U

Calls U::from(self).

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

`impl<T, U> TryFrom<U> for WeakDispatch where U: Into<T>,`

type Error = Infallible;
fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

`impl<T, U> TryInto<U> for WeakDispatch where U: TryFrom<T>,`

type Error = <U as TryFrom<T>>::Error;
fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>