Replace mutable reference with a value

1

Hi, I'm having a little trouble with a library I am working with.
The library has a struct that looks like this:

struct Foo;

impl Foo {
    fn bar(mut self) -> Self {
        // Does some stuff
    }
}

I am using Foo in a HashMap and am trying to do the following:

let ref: &mut Foo = hash_map.get_mut(&key).unwrap();
ref = ref.bar();

This doesn't work as bar takes ownership of the Foo instance. I have also tried doing std::mem::replace(ref, ref.bar()), but this doesn't work as I "cannot move out of ref because it is borrowed".

Is replacing ref with ref.bar() possible?

2

The problem is if the function panic the stack unwinding will touches invalid value. You can use take_mut crate which aborts the process unrecoverably in such case.

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3

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