SwiftUI changed how iOS apps are built. A declarative syntax and live previews make it possible to design and ship UIs faster than with UIKit alone.
Why SwiftUI?
You describe what the UI should look like and how it should behave, instead of manually updating views. The code is easier to read and maintain, and Xcode's canvas shows you the result as you type.
Your First SwiftUI View
Create a new SwiftUI file and define a view conforming to View. Use stacks (VStack, HStack, ZStack) to lay out components and modifiers like .padding() and .font() to customize the appearance.
State and Data Flow
Use @State for local view state, @Binding to pass data both ways to child views, and @ObservableObject or @StateObject for shared state. The UI stays in sync with your data automatically.
Tips for Production
Combine SwiftUI with UIKit when needed using UIViewRepresentable and UIViewControllerRepresentable. Test on multiple device sizes and enable Dynamic Type for accessibility.