16.1 UIKit and Interface Builder
To understand the meaning and advantages of SwiftUI’s declarative syntax, it helps to understand how user interface layouts were designed before the introduction of SwiftUI. Up until the introduction of SwiftUI, iOS apps were built entirely using UIKit together with a collection of associated frameworks that make up the iOS Software Development Kit (SDK).
To aid in the design of the user interface layouts that make up the screens of an app, Xcode includes a tool called Interface Builder. Interface Builder is a powerful tool that allows storyboards to be created which contain the individual scenes that make up an app (with a scene typically representing a single app screen).
The user interface layout of a scene is designed within Interface Builder by dragging components (such as buttons, labels, text fields and sliders) from a library panel to the desired location on the scene canvas. Selecting a component in a scene provides access to...
