Struct objc2::rc::Weak

pub struct Weak<T: ?Sized> { /* private fields */ }

A weak pointer to an Objective-C reference counted object.

The object is allowed to be deallocated while the weak pointer is alive, though the backing allocation for the object can only be released once all weak pointers are gone.

Useful for breaking reference cycles and safely checking whether an object has been deallocated.

Comparison to std types

This is the Objective-C equivalent of sync::Weak from the standard library, and hence is only usable on types where Retained<T> acts like sync::Arc, a.k.a. on non-mutable types.

Implementations

impl<T: Message> Weak<T>

pub fn new(obj: &T) -> Self

where T: IsRetainable,

Construct a new weak pointer that references the given object.

pub fn from_id(obj: &Retained<T>) -> Self

where T: IsIdCloneable,

Construct a new weak pointer that references the given Retained.

Soft-deprecated alias of Weak::from_retained.

pub fn from_retained(obj: &Retained<T>) -> Self

where T: IsIdCloneable,

Construct a new weak pointer that references the given Retained.

You should prefer Weak::new whenever the object is retainable.

pub fn load(&self) -> Option<Retained<T>>

Load the object into an Retained if it still exists.

Returns None if the object has been deallocated, or the Weak was created with Default::default.

Trait Implementations

impl<T: Message + IsRetainable> Clone for Weak<T>

fn clone(&self) -> Self

Make a clone of the weak pointer that points to the same object.

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

Performs copy-assignment from source.

impl<T: ?Sized> Debug for Weak<T>

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

Formats the value using the given formatter.

impl<T: Message + IsRetainable> Default for Weak<T>

fn default() -> Self

Constructs a new weak pointer that doesn’t reference any object.

Calling Self::load on the return value always gives None.

impl<T: ?Sized> Drop for Weak<T>

fn drop(&mut self)

Destroys the weak pointer.

impl<T: Message + IsIdCloneable> From<&Retained<T>> for Weak<T>

fn from(obj: &Retained<T>) -> Self

Converts to this type from the input type.

impl<T: Message + IsRetainable> From<&T> for Weak<T>

fn from(obj: &T) -> Self

Converts to this type from the input type.

impl<T: Message + IsIdCloneable> From<Retained<T>> for Weak<T>

fn from(obj: Retained<T>) -> Self

Converts to this type from the input type.

impl<T: ?Sized + RefUnwindSafe + IsIdCloneable> RefUnwindSafe for Weak<T>

impl<T: ?Sized + Sync + Send + IsIdCloneable> Send for Weak<T>

impl<T: ?Sized + Sync + Send + IsIdCloneable> Sync for Weak<T>

impl<T: ?Sized> Unpin for Weak<T>

impl<T: ?Sized + RefUnwindSafe + IsIdCloneable> UnwindSafe for Weak<T>