뷰컨트롤러 전반에 대해서는 여기가 정말 자세한거 같다. 일단 첫 문단을 읽었는데 모르던 내용이 두개나 있다. There are two ways to display a view controller onscreen: embed it in a container view controller or present it. Container view controllers provide an app’s primary navigation, but presenting view controllers is also an important navigation tool. You use direct presentation to display a new view controller on top of the current one. Ty..