option map

• https://doc.rust-lang.org/std/option/enum.Option.html#method.map
• Maps an Option<T> to Option<U> by applying a function to a contained value
• 기존 Option을 consume한다는거에 유의. 만약 옵션 타입 내부에 있는 값을 move하지 않으면서 빌려오고 싶다면 option as_ref 를 사용하면 된다.

signature

pub fn map<U, F>(self, f: F) -> Option<U>

example
Calculates the length of an Option<String> as an Option<usize>, consuming the original:

let maybe_some_string = Somefrom("Hello, World!");
// `Option::map` takes self *by value*, consuming `maybe_some_string`
let maybe_some_len = maybe_some_string.map(|s| s.len());

assert_eq!(maybe_some_len, Some(13));