Lifetimes

Code

// Lifetime annotation
fn longest<'a>(x: &'a str, y: &'a str) -> &'a str {
    if x.len() > y.len() {
        x
    } else {
        y
    }
}

// Lifetime in struct
struct Excerpt<'a> {
    part: &'a str,
}

impl<'a> Excerpt<'a> {
    fn announce(&self, msg: &str) -> &str {
        println!("{}: {}", msg, self.part);
        self.part
    }
}

// Static lifetime
fn static_example() {
    let s: &'static str = "I live forever";
    println!("{}", s);
}

fn main() {
    let s1 = String::from("long string");
    let s2 = String::from("short");
    let result = longest(s1.as_str(), s2.as_str());
    println!("Longest: {}", result);

    let novel = String::from("Call me Ishmael...");
    let first = Excerpt { part: &novel[0..4] };
    first.announce("Excerpt");
}

Explanation

Lifetimes ensure references remain valid; 'a is a lifetime parameter; 'static means the entire program duration.

More Rust Snippets