Using UIView via code or interface builder to build your own custom views

UIViews are the base building blocks of any iOS app. Think of LEGO; kids build their own buildings and blocks using tiny base blocks. The same logic is used in iOS; all UI screens you see are just a building of UIViews. All native/custom UI components extend from UIView; in other words, UIView is the base class of all UI components. To master iOS development and building the layout of any app, you have to be familiar with UIView.