[stouset]

Only if you want it to.

    #[derive(Default)]
    struct Foo {
        …
    }

    struct Bar {
        …
    }

    fn do_something(foo: Foo) -> Bar {
        # do something with Foo and return a Bar
        …
    }

    fn main() {
        let opt_foo: Option<Foo> = None;

        // panics
        let foo: Foo = opt_foo.unwrap();

        // panics, but with an error message of your choosing
        let foo: Foo = opt_foo.expect("foo was supposed to be there");

        // converts the Option (Some or None) to a Result (Ok or Err,
        // where Err can contain an error type or message and then passed
        // around or returned or whatever)
        let foo: Result<Foo> = opt_foo.ok_or("foo was supposed to be there");

        // replaces it with a value of your choosing if it's not there
        let foo: Foo = opt_foo.unwrap_or(Foo { … });

        // replaces it with the default value the type defines
        let foo: Foo = opt_foo.unwrap_or_default();

        // keeps it as `None`, or if it's actually something then
        // replaces the internal contents with the result of the
        // function call
        let bar: Option<Bar> = opt_foo.map(do_something);

        // does arbitrary logic in the match arm if foo is there
        match opt_foo {
            Some(foo) => { do something with foo },
            None      => { do something else },
        }
    }

There are a few dozen other things you can do with an Option that handle the rarer use-cases, but the above are like 95%+ of what you want.

[imron]

Rust gives you options :-)