Struct alloc::rc::Weak [−] [src]

pub struct Weak<T: ?Sized> {
    _ptr: Shared<RcBox<T>>,
}

A weak version of Rc<T>.

Weak references do not count when determining if the inner value should be dropped.

Fields

_ptr

Upgrades a weak reference to a strong reference.

Upgrades the Weak<T> reference to an Rc<T>, if possible.

Returns None if there were no strong references and the data was destroyed.

use std::rc::Rc;

let five = Rc::new(5);

let weak_five = Rc::downgrade(&five);

let strong_five: Option<Rc<_>> = weak_five.upgrade();

Unstable (downgraded_weak #30425)
: recently added

Constructs a new Weak<T> without an accompanying instance of T.

This allocates memory for T, but does not initialize it. Calling Weak::upgrade() on the return value always gives None.

#![feature(downgraded_weak)]

use std::rc::Weak;

let empty: Weak<i64> = Weak::new();