Use of as_ref() in Rust

main.rs

struct Foo {
    title: String,
}

impl Foo {
    fn new(title: &str) -> Foo {
        Foo {
            title: title.to_string(),
        }
    }
}

fn do_something(opt_foo: &Option<Foo>) -> () {
    println!(
        "f.title={}",
        opt_foo
            .as_ref()
            .map_or(
                "(none)".to_string(),
                |ref foo| foo.title.clone()))
}

fn main() {
    do_something(&Some(Foo::new("<title>")))
}