quest – Rust: Ownership

Core Intermediate

07 Ownership

The heart of Rust. These functions take ownership when they shouldn't -- borrow instead, so the caller keeps its values.

Step 3 / 3

Change sign to take the String by value, append " -- ok", and hand ownership back.

Hints

Take it by value -- mut s: String -- so the function owns it and may mutate it.
Return s as the last expression: ownership flows back to the caller.

07_ownership.rs

// BROKEN: a shared borrow can't be mutated or given away.
// Take ownership instead: accept the String by value and return it.
fn sign(s: &String) -> String {
    s.push_str(" -- ok");
    s
}

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

Reveal solution

fn sign(mut s: String) -> String {
    s.push_str(" -- ok");
    s
}