swift-expert

Swift Expert

Expert guidance for Swift development including iOS/macOS apps, SwiftUI, Combine, async/await, and Swift 5.9+ features.

Core Concepts

Modern Swift Features (5.9+)

• Async/await concurrency
• Actors for thread safety
• Property wrappers
• Result builders
• Protocols and generics
• Value types vs reference types
• Automatic Reference Counting (ARC)
• Macros (Swift 5.9+)

SwiftUI

• Declarative UI framework
• State management
• View composition
• Layout system
• Animations
• Navigation

Combine

• Reactive programming
• Publishers and subscribers
• Operators
• Error handling

SwiftUI

Basic Views

import SwiftUI

struct ContentView: View {
    @State private var name = ""
    @State private var count = 0

    var body: some View {
        VStack(spacing: 20) {
            Text("Hello, \(name.isEmpty ? "World" : name)!")
                .font(.title)
                .foregroundColor(.blue)

            TextField("Enter name", text: $name)
                .textFieldStyle(.roundedBorder)
                .padding()

            HStack {
                Button("Decrement") {
                    count -= 1
                }

                Text("\(count)")
                    .frame(minWidth: 50)

                Button("Increment") {
                    count += 1
                }
            }
            .buttonStyle(.borderedProminent)
        }
        .padding()
    }
}

State Management

// @State - local view state
struct CounterView: View {
    @State private var count = 0

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

// @Binding - pass state reference
struct ChildView: View {
    @Binding var isOn: Bool

    var body: some View {
        Toggle("Setting", isOn: $isOn)
    }
}

// @ObservableObject - external state
class UserViewModel: ObservableObject {
    @Published var user: User?
    @Published var isLoading = false
    @Published var error: Error?

    func fetchUser() async {
        isLoading = true
        defer { isLoading = false }

        do {
            user = try await APIClient.shared.fetchUser()
        } catch {
            self.error = error
        }
    }
}

struct UserView: View {
    @StateObject private var viewModel = UserViewModel()

    var body: some View {
        Group {
            if viewModel.isLoading {
                ProgressView()
            } else if let user = viewModel.user {
                UserDetailView(user: user)
            } else if let error = viewModel.error {
                ErrorView(error: error)
            }
        }
        .task {
            await viewModel.fetchUser()
        }
    }
}

// @EnvironmentObject - app-wide state
@main
struct MyApp: App {
    @StateObject private var appState = AppState()

    var body: some Scene {
        WindowGroup {
            ContentView()
                .environmentObject(appState)
        }
    }
}

struct SomeView: View {
    @EnvironmentObject var appState: AppState

    var body: some View {
        Text(appState.currentUser?.name ?? "Guest")
    }
}