Merge pull request #9 from udacity/Exercise-SwiftUI-Tasks

Exercise: SwiftUI Tasks

lesson-2-concurrency-in-iOS-apps/exercises/swiftUI-tasks/README.md

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+### Exercise: SwiftUI Tasks
+
+## Overview
+
+This exercise is a continuation of the TripJournal app. You will refactor the app to use SwiftUI's `Task` modifier for managing asynchronous operations, ensuring that tasks are properly managed and canceled when no longer needed.
+
+#### Objectives
+- Use the `Task` modifier to manage asynchronous operations.
+- Cancel tasks when they are no longer needed.
+- Ensure state changes and UI updates are properly handled.
+
+#### Instructions
+
+1. **Starter:**
+   - Navigate to the starter folder and open `TripJournal.xcodeproj`.
+   - Your task is to fill in the missing code as indicated by comments in the Swift files (`AuthView.swift`, `TripList.swift`, `TripForm.swift`).
+
+2. **Solution:**
+   - After you complete the exercise, or if you need to check your work, you can find the complete code in the solution folder.
+   - Compare your solution with the completed code to understand different approaches or to debug any issues you encountered.
+
+#### Setup
+- Ensure you have the latest version of Xcode installed on your Mac.
+- Open the Xcode project from the `starter` folder to begin the exercise.
+
+Feel free to reach out if you encounter any difficulties or have questions regarding the exercises.
+
+Happy coding!

lesson-2-concurrency-in-iOS-apps/exercises/swiftUI-tasks/solution/TripJournal.xcodeproj/project.xcworkspace/xcshareddata/IDEWorkspaceChecks.plist

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+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>IDEDidComputeMac32BitWarning</key>
+	<true/>
+</dict>
+</plist>

lesson-2-concurrency-in-iOS-apps/exercises/swiftUI-tasks/solution/TripJournal/App.swift

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+import SwiftUI
+
+@main
+struct TripJournalApp: App {
+    var body: some Scene {
+        WindowGroup {
+            RootView(service: JournalServiceLive())
+        }
+    }
+}

lesson-2-concurrency-in-iOS-apps/exercises/swiftUI-tasks/solution/TripJournal/Assets.xcassets/AccentColor.colorset/Contents.json

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+{
+  "colors" : [
+    {
+      "color" : {
+        "platform" : "universal",
+        "reference" : "systemPurpleColor"
+      },
+      "idiom" : "universal"
+    }
+  ],
+  "info" : {
+    "author" : "xcode",
+    "version" : 1
+  }
+}

lesson-2-concurrency-in-iOS-apps/exercises/swiftUI-tasks/solution/TripJournal/Assets.xcassets/AppIcon.appiconset/Contents.json

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+{
+  "images" : [
+    {
+      "filename" : "icon.png",
+      "idiom" : "universal",
+      "platform" : "ios",
+      "size" : "1024x1024"
+    }
+  ],
+  "info" : {
+    "author" : "xcode",
+    "version" : 1
+  }
+}

lesson-2-concurrency-in-iOS-apps/exercises/swiftUI-tasks/solution/TripJournal/Assets.xcassets/AuthHeader.imageset/Contents.json

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+{
+  "images" : [
+    {
+      "filename" : "icon.png",
+      "idiom" : "universal"
+    }
+  ],
+  "info" : {
+    "author" : "xcode",
+    "version" : 1
+  },
+  "properties" : {
+    "template-rendering-intent" : "original"
+  }
+}

lesson-2-concurrency-in-iOS-apps/exercises/swiftUI-tasks/solution/TripJournal/Assets.xcassets/Contents.json

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+{
+  "info" : {
+    "author" : "xcode",
+    "version" : 1
+  }
+}

lesson-2-concurrency-in-iOS-apps/exercises/swiftUI-tasks/solution/TripJournal/Auth/AuthView.swift

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+import SwiftUI
+
+struct AuthView: View {
+    /// Describes validation errors that might occur locally in the form.
+    struct ValidationError: LocalizedError {
+        var errorDescription: String?
+
+        static let emptyUsername = Self(errorDescription: "Username is required.")
+        static let emptyPassword = Self(errorDescription: "Password is required.")
+    }
+
+    @State private var username: String = ""
+    @State private var password: String = ""
+    @State private var isLoading = false
+    @State private var error: Error?
+    @Environment(\.journalService) private var journalService
+
+    @State private var task: Task<Void, Never>? = nil
+
+    // MARK: - Body
+
+    var body: some View {
+        Form {
+            Section(
+                content: inputs,
+                header: header,
+                footer: buttons
+            )
+        }
+        .loadingOverlay(isLoading)
+        .alert(error: $error)
+        .task {
+            await checkTokenExpiration()
+        }
+        .onDisappear {
+            task?.cancel()
+        }
+    }
+
+    // MARK: - Views
+
+    private func header() -> some View {
+        Image(.authHeader)
+            .resizable()
+            .frame(width: 100, height: 100)
+            .clipShape(RoundedRectangle(cornerRadius: 25))
+            .frame(maxWidth: .infinity, alignment: .center)
+            .padding(.top, 30)
+            .padding(.bottom, 70)
+    }
+
+    @ViewBuilder
+    private func inputs() -> some View {
+        TextField("Username", text: $username)
+            .autocorrectionDisabled()
+            .textInputAutocapitalization(.never)
+            .textContentType(.username)
+        SecureField("Password", text: $password)
+            .autocorrectionDisabled()
+            .textInputAutocapitalization(.never)
+            .textContentType(.password)
+    }
+
+    private func buttons() -> some View {
+        VStack(alignment: .center, spacing: 10) {
+            Button(
+                action: {
+                    task = Task {
+                        await logIn()
+                    }
+                },
+                label: {
+                    Text("Log In")
+                        .frame(maxWidth: .infinity, alignment: .center)
+                }
+            )
+            .buttonBorderShape(.capsule)
+            .buttonStyle(.borderedProminent)
+
+            Button(
+                action: {
+                    task = Task {
+                        await register()
+                    }
+                },
+                label: {
+                    Text("Create Account")
+                        .frame(maxWidth: .infinity, alignment: .center)
+                }
+            )
+            .buttonBorderShape(.capsule)
+            .buttonStyle(.bordered)
+        }
+        .padding()
+    }
+
+    // MARK: - Networking
+
+    private func validateForm() throws {
+        if username.nonEmpty == nil {
+            throw ValidationError.emptyUsername
+        }
+        if password.nonEmpty == nil {
+            throw ValidationError.emptyPassword
+        }
+    }
+
+    private func logIn() async {
+        isLoading = true
+        do {
+            try validateForm()
+            try await journalService.logIn(username: username, password: password)
+        } catch {
+            self.error = error
+        }
+        isLoading = false
+    }
+
+    private func register() async {
+        isLoading = true
+        do {
+            try validateForm()
+            try await journalService.register(username: username, password: password)
+        } catch {
+            self.error = error
+        }
+        isLoading = false
+    }
+
+    private func checkTokenExpiration() async {
+        DispatchQueue.main.async {
+            guard journalService.tokenExpired else {
+                return
+            }
+            error = SessionError.expired
+        }
+    }
+}

lesson-2-concurrency-in-iOS-apps/exercises/swiftUI-tasks/solution/TripJournal/Helpers/KeychainHelper.swift

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+//
+//  KeychainHelper.swift
+//  TripJournal
+//
+//  Created by Jesus Guerra on 5/17/24.
+//
+
+import Foundation
+import Security
+
+class KeychainHelper {
+    static let shared = KeychainHelper()
+    private let serviceName = "com.TripJournal.service"
+    private let accountName = "authToken"
+
+    private init() {}
+
+    func saveToken(_ token: Token) throws {
+        let tokenData = try JSONEncoder().encode(token)
+        let query: [String: Any] = [
+            kSecClass as String: kSecClassGenericPassword,
+            kSecAttrService as String: serviceName,
+            kSecAttrAccount as String: accountName,
+            kSecValueData as String: tokenData,
+            kSecAttrAccessible as String: kSecAttrAccessibleWhenUnlocked
+        ]
+
+        SecItemDelete(query as CFDictionary) // Delete any existing item
+        let status = SecItemAdd(query as CFDictionary, nil)
+
+        guard status == errSecSuccess else {
+            throw KeychainError.unableToSaveToken
+        }
+    }
+
+    func getToken() throws -> Token? {
+        let query: [String: Any] = [
+            kSecClass as String: kSecClassGenericPassword,
+            kSecAttrService as String: serviceName,
+            kSecAttrAccount as String: accountName,
+            kSecReturnData as String: kCFBooleanTrue!,
+            kSecMatchLimit as String: kSecMatchLimitOne
+        ]
+
+        var dataTypeRef: AnyObject? = nil
+        let status = SecItemCopyMatching(query as CFDictionary, &dataTypeRef)
+
+        guard status == errSecSuccess else {
+            return nil
+        }
+
+        guard let data = dataTypeRef as? Data else {
+            return nil
+        }
+
+        return try JSONDecoder().decode(Token.self, from: data)
+    }
+
+    func deleteToken() throws {
+        let query: [String: Any] = [
+            kSecClass as String: kSecClassGenericPassword,
+            kSecAttrService as String: serviceName,
+            kSecAttrAccount as String: accountName
+        ]
+
+        let status = SecItemDelete(query as CFDictionary)
+
+        guard status == errSecSuccess else {
+            throw KeychainError.unableToDeleteToken
+        }
+    }
+
+    enum KeychainError: Error {
+        case unableToSaveToken
+        case unableToDeleteToken
+    }
+}
+

lesson-2-concurrency-in-iOS-apps/exercises/swiftUI-tasks/solution/TripJournal/JournalService/JournalService+Environment.swift

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+import SwiftUI
+
+private struct JournalServiceKey: EnvironmentKey {
+    static var defaultValue: JournalService = JournalServiceLive()
+}
+
+extension EnvironmentValues {
+    /// A service that can used to interact with the trip journal API.
+    var journalService: JournalService {
+        get { self[JournalServiceKey.self] }
+        set { self[JournalServiceKey.self] = newValue }
+    }
+}