Try It Yourself - SyntaxStudy Editor

HTML / CSS / JS

// Lifetime annotation: the returned reference lives as long as
// the shorter-lived of x and y.
fn longest<'a>(x: &'a str, y: &'a str) -> &'a str {
    if x.len() >= y.len() { x } else { y }
}

// Struct holding a reference must declare a lifetime parameter
struct Excerpt<'a> {
    part: &'a str,
}

impl<'a> Excerpt<'a> {
    // Elided: &self has lifetime 'a, return shares 'a
    fn content(&self) -> &str {
        self.part
    }
}

fn main() {
    let s1 = String::from("long string is long");
    let result;
    {
        let s2 = String::from("xyz");
        result = longest(s1.as_str(), s2.as_str());
        println!("longest = {result}");
    }
    // result cannot be used here — s2 dropped above

// Struct with a reference
    let novel = String::from("Call me Ishmael. Some years ago...");
    let first_sentence = novel.split('.').next().unwrap();
    let ex = Excerpt { part: first_sentence };
    println!("excerpt: {}", ex.content());

// 'static lifetime — valid for entire program
    let s: &'static str = "I am embedded in the binary";
    println!("{s}");
}