Swift iOS

Building native iOS apps with Swift and SwiftUI.

Quick Start

# Xcode -> New Project -> SwiftUI App
# or: swift package init

When to Use

• Native iOS/macOS/watchOS apps
• Modern SwiftUI interfaces
• Teams using Swift concurrency
• Apps for the App Store

Best Practices

SwiftUI Views

• Build declarative views from state
• Use `@State`, `@Binding`, `@Observable`
• Keep views small and composable
• Use SwiftUI navigation and sheets

State Management

• Model state with `@Observable` classes
• Derive views from published state
• Use environment for shared objects
• Avoid storing derived data

Concurrency

• Use async/await and actors
• Scope tasks to view lifecycle
• Use `Task` and `MainActor` for UI
• Avoid data races with actors

Networking & Persistence

• Fetch with async/await
• Decode with Codable
• Cache with SwiftData or Core Data
• Handle errors and retries

Dependencies

# Swift Package Manager
swift package init

Examples

import SwiftUI

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

    var body: some View {
        VStack(spacing: 12) {
            Text("Count: \(count)")
                .font(.headline)
            Button("Add") { count += 1 }
                .buttonStyle(.borderedProminent)
        }
    }
}

// Observable model
import Observation

@Observable
final class UserStore {
    var users: [User] = []
    var isLoading = false

    func load() async {
        isLoading = true
        defer { isLoading = false }
        users = try! await api.fetchUsers()
    }
}

// Async networking with Codable
struct User: Codable, Identifiable {
    let id: Int
    let name: String
}

func fetchUsers() async throws -> [User] {
    let (data, _) = try await URLSession.shared.data(from: url)
    return try JSONDecoder().decode([User].self, from: data)
}

// Navigation
NavigationStack {
    List(store.users) { user in
        NavigationLink(user.name) { UserDetailView(user: user) }
    }
}

Step-by-Step

1. Create a SwiftUI project.

2. Model the domain with Codable types.

3. Build views from `@Observable` state.

4. Add navigation and sheets.

5. Fetch data with async/await.

6. Persist with SwiftData when needed.

7. Handle errors and loading states.

8. Test with XCTest/XCUITest.

Validation

1. Project builds without errors

2. Views react to state changes

3. Async work is scoped and safe

4. Navigation works end to end

5. Unit/UI tests pass

Troubleshooting

• Main actor errors: mark UI code @MainActor.
• Data races: use actors for shared state.
• Broken decoding: align Codable with the API shape.