Struct WeakDispatch

pub struct WeakDispatch { /* private fields */ }

Available on crate features dep_tracing and alloc only.

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. 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

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

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

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for WeakDispatch

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

Formats the value using the given formatter.