lazy loading problem

playground.rs

struct Context {
    foo: Option<String>,
    bar: Option<String>
}

impl Context {
    fn new() -> Self {
        Context {
            foo: None,
            bar: None
        }
    }

    fn foo(&mut self) -> &str {
        if self.foo.is_none() {
            let message = String::from("foo");
            self.foo = Some(message);
        }

        self.foo.as_ref().unwrap()
    }

    fn bar(&mut self) -> &str {
        if self.bar.is_none() {
            let message = String::from("bar");
            self.bar = Some(message);
        }

        self.bar.as_ref().unwrap()
    }
}

fn print(context: &mut Context) {
    let foo = context.foo();
    let bar = context.bar();

    println!("{}{}", foo, bar);
}

fn main() {
    let mut context = Context::new();

    print(&mut context);
}