Is there a shared pointer from which it is possible to steal data?

Question

I want to share a structure Foo between several other structures with the ability to extract this data. All other holders of this structure will see the value disappear.

Pseudocode:

if boo.ref_to_foo.is_valid() {
   let foo: Foo = boo.ref_to_foo.steal(); //1
} else {
   //after executing 1 one time all come here 
}

I do not need multithreading.

Is Rc<RefCell<Foo>> what I want? Deref for Rc + RefCell::borrow_mut + Option::take, or maybe some simpler way to achieve what I want?

Shepmaster · Accepted Answer · 2017-08-14T15:40:32.590

Is there a shared pointer from which it is possible to steal data?

No, but you have all the building blocks you need to create one. Since you

want to change the value, you need the interior mutability provided by RefCell.
want to share ownership, you need Rc.
want to have the possibility of having a value or not a value, you need Option.

use std::rc::Rc;
use std::cell::RefCell;

struct Foo;

fn main() {
    let foo1 = Rc::new(RefCell::new(Some(Foo)));
    let foo2 = foo1.clone();

    if foo1.borrow().is_some() {
        let stolen = foo1.borrow_mut().take();
    } else {
        println!("Already stolen!")
    }

    if foo2.borrow().is_some() {
        let stolen = foo2.borrow_mut().take();
    } else {
        println!("Already stolen!")
    }
}

If you felt like it, you could probably wrap all this up into a single type.

Is there a shared pointer from which it is possible to steal data?

1 Answers1