20170617_5.rs

impl<'a, 'r> FromRequest<'a, 'r> for Lang {
    type Error = ();

    fn from_request(request: &'a Request<'r>) -> Outcome<Lang, ()> {
        match request.cookies().get_private("lang") {
            Some(r) => {
                match Lang::from_str(r.value()) {
                    Ok(l) => Success(l),
                    Err(_) => Success(Lang::default()),
                }
            }
            None => Success(Lang::default()),
        }
    }
}