옵셔널 바인딩

https://s3-us-west-2.amazonaws.com/secure.notion-static.com/4ed8d8ca-e75d-4f37-9cc2-9614dcf40be2/_2020-01-14__3.07.19.png

옵셔널 바인딩 if-let

https://s3-us-west-2.amazonaws.com/secure.notion-static.com/46f8e1c7-31ac-4e8f-88a9-7a1ba1a3cf13/_2020-01-14__3.08.28.png

여러 optional 동시 binding

https://s3-us-west-2.amazonaws.com/secure.notion-static.com/ed086957-e0dc-4972-bdec-8174d3fde27f/_2020-01-14__3.13.54.png

강제 추출

https://s3-us-west-2.amazonaws.com/secure.notion-static.com/7920a942-3f12-4ba6-b19b-2b1101b0772f/_2020-01-14__3.16.15.png