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skills/ios-swift-expert/references/code-examples.md

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+# iOS Development Code Examples
+
+Complete implementation examples for common iOS and macOS development patterns.
+
+## SwiftUI View with Proper State Management
+
+```swift
+import SwiftUI
+
+struct UserProfileView: View {
+    @StateObject private var viewModel = UserProfileViewModel()
+    @Environment(\.dismiss) private var dismiss
+
+    var body: some View {
+        NavigationStack {
+            ScrollView {
+                VStack(alignment: .leading, spacing: 16) {
+                    // Profile content
+                    AsyncImage(url: viewModel.avatarURL) { image in
+                        image
+                            .resizable()
+                            .scaledToFill()
+                    } placeholder: {
+                        ProgressView()
+                    }
+                    .frame(width: 100, height: 100)
+                    .clipShape(Circle())
+
+                    Text(viewModel.userName)
+                        .font(.title)
+                        .accessibilityAddTraits(.isHeader)
+                }
+                .padding()
+            }
+            .navigationTitle("Profile")
+            .toolbar {
+                ToolbarItem(placement: .navigationBarTrailing) {
+                    Button("Done") {
+                        dismiss()
+                    }
+                }
+            }
+            .task {
+                await viewModel.loadProfile()
+            }
+        }
+    }
+}
+```
+
+## MVVM ViewModel with Async/Await
+
+```swift
+import Foundation
+import Combine
+
+@MainActor
+final class UserProfileViewModel: ObservableObject {
+    @Published private(set) var userName: String = ""
+    @Published private(set) var avatarURL: URL?
+    @Published private(set) var isLoading = false
+    @Published private(set) var error: Error?
+
+    private let userService: UserServiceProtocol
+
+    init(userService: UserServiceProtocol = UserService()) {
+        self.userService = userService
+    }
+
+    func loadProfile() async {
+        isLoading = true
+        error = nil
+
+        do {
+            let profile = try await userService.fetchCurrentUser()
+            userName = profile.name
+            avatarURL = profile.avatarURL
+        } catch {
+            self.error = error
+        }
+
+        isLoading = false
+    }
+}
+
+// Protocol for dependency injection and testing
+protocol UserServiceProtocol {
+    func fetchCurrentUser() async throws -> UserProfile
+}
+```
+
+## Core Data Stack with Modern Concurrency
+
+```swift
+import CoreData
+
+final class PersistenceController {
+    static let shared = PersistenceController()
+
+    let container: NSPersistentContainer
+
+    private init() {
+        container = NSPersistentContainer(name: "AppModel")
+        container.loadPersistentStores { description, error in
+            if let error = error {
+                fatalError("Unable to load persistent stores: \(error)")
+            }
+        }
+        container.viewContext.automaticallyMergesChangesFromParent = true
+    }
+
+    func save() async throws {
+        let context = container.viewContext
+        guard context.hasChanges else { return }
+
+        try await context.perform {
+            try context.save()
+        }
+    }
+
+    func backgroundContext() -> NSManagedObjectContext {
+        let context = container.newBackgroundContext()
+        context.mergePolicy = NSMergeByPropertyObjectTrumpMergePolicy
+        return context
+    }
+}
+```
+
+## Proper Memory Management with Closures
+
+```swift
+import UIKit
+
+final class DataManager {
+    private var completionHandlers: [String: (Result<Data, Error>) -> Void] = [:]
+
+    func fetchData(forKey key: String, completion: @escaping (Result<Data, Error>) -> Void) {
+        completionHandlers[key] = completion
+
+        URLSession.shared.dataTask(with: URL(string: "https://example.com")!) { [weak self] data, response, error in
+            guard let self = self else { return }
+
+            if let error = error {
+                self.completionHandlers[key]?(.failure(error))
+            } else if let data = data {
+                self.completionHandlers[key]?(.success(data))
+            }
+
+            self.completionHandlers[key] = nil
+        }.resume()
+    }
+}
+```