Trait WeakElement

pub trait WeakElement {
    type Strong;

    // Required methods
    fn new(view: &Self::Strong) -> Self;
    fn view(&self) -> Option<Self::Strong>;

    // Provided methods
    fn is_expired(&self) -> bool { ... }
    fn clone(view: &Self::Strong) -> Self::Strong
       where Self: Sized { ... }
}

Interface for elements that can be stored in weak hash tables.

This trait applies to the weak version of a reference-counted pointer; it can be used to convert a weak pointer into a strong pointer and back. For example, the impl for std::rc::Weak<T> defines the Strong associated type as std::rc::Rc<T>. Then method new can be used to downgrade an Rc<T> to a Weak<T>, and method view can be used to upgrade a Weak<T> into an Rc<T>, if it’s still alive. If we think of the weak pointer as what is stored, then the strong pointer is a temporary view of it.

Required Associated Types

type Strong

The type at which a weak element can be viewed.

For example, for std::rc::Weak<T>, this will be std::rc::Rc<T>.

Required Methods

fn new(view: &Self::Strong) -> Self

Constructs a weak pointer from a strong pointer.

This is usually implemented by a downgrade method.

fn view(&self) -> Option<Self::Strong>

Acquires a strong pointer from a weak pointer.

This is usually implemented by an upgrade method.

Provided Methods

fn is_expired(&self) -> bool

Is the given weak element expired?

The default implemention checks whether a strong pointer can be obtained via view.

fn clone(view: &Self::Strong) -> Self::Strong

where Self: Sized,

Clones a strong pointer.

The default implementation uses new and view; you should override it.

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Implementations on Foreign Types

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

type Strong = Rc<T>

fn new(view: &Self::Strong) -> Self

fn view(&self) -> Option<Self::Strong>

fn clone(view: &Self::Strong) -> Self::Strong

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

type Strong = Arc<T>

fn new(view: &Self::Strong) -> Self

fn view(&self) -> Option<Self::Strong>

fn clone(view: &Self::Strong) -> Self::Strong

Implementors