Lifetimes

Lifetimes#

A lifetime 'a is a region annotation telling the compiler how long a reference must remain valid. Often elided; explicit when ambiguous.

Function with two borrowed inputs that share a lifetime.

fn longest<'a>(a: &'a str, b: &'a str) -> &'a str {
    if a.len() > b.len() { a } else { b }
}

Struct with a borrowed field; the struct cannot outlive the borrow.

struct Holder<'a> { name: &'a str }

The static lifetime 'static lasts the whole program (string literals, static items).

let s: &'static str = "hello";