How ownership works with match expressions

In a match expression, the value being matched is moved into the pattern, transferring ownership to the matched arm.

enum Message {
    Quit,
    Move { x: i32, y: i32 },
    Write(String),
    ChangeColor(u8, u8, u8),
}

fn main() {
    let msg = Message::Write(String::from("hello"));
    
    match msg {
        Message::Write(text) => {
            // `text` owns the String here; `msg` is consumed
            println!("Text: {text}");
        },
        _ => {},
    }
    // msg cannot be used here; it was moved into the match
}

If you need to use the value after the match, match on a reference (&msg) instead to borrow it.

When you use a match statement, Rust moves the data into the specific case that matches, meaning the original variable is no longer available afterward. Think of it like handing a physical object to a specific person; once they have it, you don't have it anymore. To keep the original, you must match on a reference (a pointer) to the data instead of the data itself.