You don't need to specify a return type in scala. In this case the return type is inferred as Option[Long]. You are correct about the exception if the cookie's

You don't need to specify a return type in scala. In this case the return type is inferred as Option[Long]. You are correct about the exception if the cookie's value can't be parsed as a Long. You might instead write the code as: def getUserId()(implicit request: RequestHeader): Option[Long] = { request.cookies.get("uid") .flatMap(cookie => Try(cookie.value.toLong).toOption) .filter(_ > 0) } or, equivalently: def getUserId()(implicit request: RequestHeader): Option[Long] = for { cookie <- request.cookies.get("uid") value <- Try(cookie.value.toLong).toOption if value > 0 } yield value