SwiftUI

Declarative UI framework for Apple platforms.

When to Use

• iOS/iPadOS/macOS development
• Declarative UI patterns
• Cross-Apple platform apps
• Modern Swift development

Quick Start

import SwiftUI

struct ContentView: View {
    var body: some View {
        VStack {
            Text("Hello, SwiftUI!")
                .font(.largeTitle)
            Button("Tap me") {
                print("Tapped!")
            }
        }
    }
}

Core Concepts

State Management

struct Counter: View {
    @State private var count = 0

    var body: some View {
        VStack {
            Text("Count: \(count)")
            Button("Increment") {
                count += 1
            }
        }
    }
}

// Observable model (iOS 17+)
@Observable class UserModel {
    var name: String = ""
    var isLoggedIn: Bool = false
}

struct ProfileView: View {
    @Environment(UserModel.self) var user

    var body: some View {
        Text("Hello, \(user.name)")
    }
}

Navigation

import SwiftUI

struct ContentView: View {
    var body: some View {
        NavigationStack {
            List(users) { user in
                NavigationLink(value: user) {
                    Text(user.name)
                }
            }
            .navigationTitle("Users")
            .navigationDestination(for: User.self) { user in
                UserDetailView(user: user)
            }
        }
    }
}

Common Patterns

Lists & Data

struct UserList: View {
    let users: [User]

    var body: some View {
        List(users) { user in
            HStack {
                AsyncImage(url: user.avatarURL) { image in
                    image.resizable().frame(width: 40, height: 40)
                } placeholder: {
                    ProgressView()
                }
                VStack(alignment: .leading) {
                    Text(user.name).font(.headline)
                    Text(user.email).font(.caption)
                }
            }
        }
    }
}

Async Data

struct UserView: View {
    let userId: String
    @State private var user: User?
    @State private var isLoading = true

    var body: some View {
        Group {
            if isLoading {
                ProgressView()
            } else if let user {
                UserCard(user: user)
            }
        }
        .task {
            user = try? await fetchUser(id: userId)
            isLoading = false
        }
    }
}

Best Practices

Do:

• Use @Observable for models (iOS 17+)
• Prefer small, composable views
• Use environment for dependency injection
• Test with PreviewProvider

Don't:

• Put complex logic in views
• Use force unwrapping
• Ignore accessibility
• Skip dark mode support

Troubleshooting

Issue	Cause	Solution
View not updating	State issue	Check property wrappers
Preview crash	Missing data	Add mock data
Navigation broken	Stack issue	Check NavigationStack

References

• SwiftUI Documentation
• Hacking with Swift