Annotating Lifetimes in Functions and Structs

Annotating Lifetimes in Functions and Structs

When a function returns a reference that could come from multiple inputs, explicit lifetime annotations are required:

// The returned reference is guaranteed valid for the intersection of 'a
fn longest<'a>(x: &'a str, y: &'a str) -> &'a str {
    if x.len() > y.len() { x } else { y }
}

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

fn main() {
    let string1 = String::from("desk configuration");
    let result;
    {
        let string2 = String::from("orders");
        result = longest(string1.as_str(), string2.as_str());
        println!("Longest string: {}", result);
    }
}