Giới thiệu SwiftUI

// ❌ Imperative (UIKit)
let label = UILabel()
label.text = "Hello"
label.textColor = .blue
view.addSubview(label)
 
// ✅ Declarative (SwiftUI)
Text("Hello")
    .foregroundColor(.blue)

import SwiftUI
 
struct ContentView: View {
    var body: some View {
        VStack {
            Text("Hello, SwiftUI!")
                .font(.largeTitle)
                .foregroundColor(.blue)
            
            Button("Tap Me") {
                print("Button tapped!")
            }
            .padding()
            .background(.blue)
            .foregroundColor(.white)
            .cornerRadius(10)
        }
    }
}
 
#Preview {
    ContentView()
}

protocol View {
    associatedtype Body: View
    @ViewBuilder var body: Self.Body { get }
}

Text("Hello")
    .font(.title)           // Font
    .foregroundColor(.red)  // Màu chữ
    .padding()              // Padding
    .background(.yellow)    // Background
    .cornerRadius(8)        // Bo góc

// Khác nhau:
Text("A").padding().background(.red)    // Background bao padding
Text("B").background(.red).padding()    // Background chỉ text

#Preview {
    ContentView()
}
 
// Multiple previews
#Preview("Light Mode") {
    ContentView()
        .preferredColorScheme(.light)
}
 
#Preview("Dark Mode") {
    ContentView()
        .preferredColorScheme(.dark)
}