What Is SwiftUI

SwiftUI is Apple's framework for building app screens in Swift. You describe what the screen shows, and SwiftUI draws it and redraws it whenever your data changes.

A piece of screen is a view: a struct that conforms to View and has a body property. The body returns what the view shows:

struct ContentView: View {
    var body: some View {
        Text("Hello, World!")
    }
}

Text is a view that shows a line of text. some View means the body returns one particular kind of view, and Swift works out which kind from the code inside.

The preview next to the editor renders your view each time you change the code, so you see the result of every edit.