Complete Challenge 3

> Our app silently fails when errors occur during biometric authentication. Add code to show those errors in an alert. But be careful: you can only add one alert() modifier to each view.

day-068/Projects/PlaceCase/PlaceCase/Data/State/AppState.swift

@@ -14,7 +14,7 @@ import LocalAuthentication
 
 
 struct AppState {
-    var authenticationService: AuthenticatingService
+    var authenticationService: AuthenticationService
     var locationCollectionsState: LocationCollectionsState
     var wikiPagesState: WikiPagesState
     
@@ -24,7 +24,7 @@ struct AppState {
     
     
     init(
-        authenticationService: AuthenticatingService = AuthenticationService(laContextType: LAContext.self),
+        authenticationService: AuthenticationService = AuthenticationService(laContextType: LAContext.self),
         locationCollectionsState: LocationCollectionsState = .init(),
         wikiPagesState: WikiPagesState = .init()
     ) {

day-068/Projects/PlaceCase/PlaceCase/Reusables/AuthenticationService.swift

@@ -24,19 +24,12 @@ extension LAContext: LAContextType {}
 
 
 
-protocol AuthenticatingService {
+class AuthenticationService {
-    
-    /// - Parameter reason: The app-provided reason for requesting authentication,
-    ///     which displays in the authentication dialog presented to the user.
-    func authenticate(reason: String) -> AnyPublisher<Void, Error>
-}
-
-
-
-final class AuthenticationService: AuthenticatingService {
     static let authReason = "Please authenticate to unlock this app and access saved locations."
     
-    enum Error: Swift.Error {
+    enum Error: Swift.Error, Identifiable {
+        var id: String { self.localizedDescription }
+        
         case noBiometricsEnabled(Swift.Error?)
         case evaluationFailed(Swift.Error?)
     }
@@ -46,12 +39,14 @@ final class AuthenticationService: AuthenticatingService {
     private var context: LAContextType?
 
     
-    init(laContextType: LAContextType.Type) {
+    init(laContextType: LAContextType.Type = LAContext.self) {
         self.laContextType = laContextType
     }
     
     
-    func authenticate(reason: String) -> AnyPublisher<Void, Swift.Error> {
+    /// - Parameter reason: The app-provided reason for requesting authentication,
+    ///     which displays in the authentication dialog presented to the user.
+    func authenticate(reason: String) -> AnyPublisher<Void, Error> {
         let context = laContextType.init()
         self.context = context
         
@@ -94,8 +89,8 @@ final class AuthenticationService: AuthenticatingService {
 
 extension SampleData {
     
-    class AuthService: AuthenticatingService {
+    class AuthService: AuthenticationService {
-        func authenticate(reason: String) -> AnyPublisher<Void, Error> {
+        override func authenticate(reason: String) -> AnyPublisher<Void, Error> {
             Empty().eraseToAnyPublisher()
         }
     }

day-068/Projects/PlaceCase/PlaceCase/Scenes/LocationCollectionsContainerView.swift

@@ -30,6 +30,7 @@ extension LocationCollectionsContainerView {
             }
         }
         .navigationBarTitle("PlaceCase")
+        .alert(item: $viewModel.authenticationError) { _ in self.authenticationErrorAlert }
     }
 }
 
@@ -70,6 +71,15 @@ extension LocationCollectionsContainerView {
         }
         .padding()
     }
+    
+    
+    private var authenticationErrorAlert: Alert {
+        .init(
+            title: Text(viewModel.authenticationErrorAlertTitle),
+            message: Text(viewModel.authenticationErrorAlertBody),
+            dismissButton: .default(Text("OK"))
+        )
+    }
 }
 
 

day-068/Projects/PlaceCase/PlaceCase/Scenes/LocationCollectionsContainerViewModel.swift

@@ -14,20 +14,19 @@ import Combine
 final class LocationCollectionsContainerViewModel: ObservableObject {
     private var subscriptions = Set<AnyCancellable>()
 
-    private let authService: AuthenticatingService
+    private let authService: AuthenticationService
     
 
     // MARK: - Published Properties
     @Published var isAuthenticated: Bool = false
+    @Published var authenticationError: AuthenticationService.Error? = nil
 
 
     // MARK: - Init
     init(
-        authService: AuthenticatingService
+        authService: AuthenticationService
     ) {
         self.authService = authService
-        
-        setupSubscribers()
     }
 }
 
@@ -49,7 +48,7 @@ extension LocationCollectionsContainerViewModel {
                     switch completion {
                     case .failure(let error):
                         DispatchQueue.main.async { [weak self] in
-                            print("Authentication failed: \(error)")
+                            self?.authenticationError = error
                             self?.isAuthenticated = false
                          }
                     default:
@@ -67,11 +66,25 @@ extension LocationCollectionsContainerViewModel {
     }
 }
 
+// MARK: - Computed
+extension LocationCollectionsContainerViewModel {
+    
+    var authenticationErrorAlertTitle: String { "Authentication Failed" }
+    
+    var authenticationErrorAlertBody: String {
+        guard let error = authenticationError else { return "" }
+        
+        switch error {
+        case .noBiometricsEnabled:
+            return "No Biomentric authentication is enabled on this device."
+        case .evaluationFailed(_):
+            return "An error occured while attempting evaluation."
+        }
+    }
+}
+
 
 
 // MARK: - Private Helpers
 private extension LocationCollectionsContainerViewModel {
-
-    func setupSubscribers() {
-    }
 }