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. 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.

Layout

Note: Most layout information is completely unstable and may even differ between compilations. The only exception is types with certain repr(...) attributes. Please see the Rust Reference's “Type Layout” chapter for details on type layout guarantees.

Size: 24 bytes