quest – Rust: Moving out

Borrow checker Advanced

26 Moving out

You can't move a value out from behind a reference -- that would leave a hole. The fix is to swap something valid into its place and hand back the old value. std gives you take for exactly this.

Step 2 / 2

Fix Slot::take: take the item out of &mut self, leaving None behind.

Hints

Option::take does exactly this: self.item.take().

26_move_out.rs

struct Slot { item: Option<String> }

impl Slot {
    // BROKEN: you can't move `item` out from behind &mut self.
    // Run it to see the error, then use Option::take.
    fn take(&mut self) -> Option<String> {
        let taken = self.item;
        taken
    }
}

Reset to starterCompiled in a sandbox; hidden checks must pass.

Reveal solution

struct Slot { item: Option<String> }

impl Slot {
    fn take(&mut self) -> Option<String> {
        self.item.take()
    }
}