swift GCD concurrency Petpion async/await Actor Task WWDC2022 await async WWDC2015 signInApple appleLogin tuist swinject letsSwift iOS취업준비 Sendable FirebaseStorage MainActor mainRunLoop updateCycle NetWork Activity Indicator Progress Indicator Scope Bar Search Bar kakaologin CollectionView multithreading codingtest 앱최적화 Autolayout debounce cleanarchitecture 당근마켓 WWDC2017 firebase activity indicator WWDC2016 navigationbar oauth2.0 Date Picker ImageCache programmers concurrent hig status bar leak picker semaphore AppStore OAuth progress bar 모듈화 queue Developer thread memory group display Constraints 개인프로젝트 Instruments Apple