StewartLynch · June 22, 2022 21:50 · Jun 22, 2022
diff --git a/For @kadanas b/For @kadanas
@@ -0,0 +1,74 @@
+//
+// Created for ErrorAlert
+// by Stewart Lynch on 2022-06-22
+// Using Swift 5.0
+//
+// Follow me on Twitter: @StewartLynch
+// Subscribe on YouTube: https://youTube.com/StewartLynch
+//
+
+import SwiftUI
+
+struct ContentView: View {
+    @StateObject private var viewModel = ViewModel()
+    var body: some View {
+        VStack {
+            Text(viewModel.authenticationStatus)
+            Button {
+                try? viewModel.authenticate()
+            } label: {
+                Text("Login")
+            }
+            .buttonStyle(.borderedProminent)
+        }
+        .alert(item: $viewModel.alertString) { alertString in
+            Alert(title: Text("Login Error"),
+                  message: Text(alertString.errorString))
+        }
+    }
+}
+
+struct ContentView_Previews: PreviewProvider {
+    static var previews: some View {
+        ContentView()
+    }
+}
+
+
+class ViewModel: ObservableObject {
+    @Published var authenticationStatus = "Please Log in"
+    @Published var alertString: AlertString?
+
+
+    enum AuthenticationError: Error {
+        case failed
+    }
+
+    struct AlertString: Identifiable {
+        let errorString: String
+        var id: String {
+            errorString
+        }
+    }
+
+    func authenticate() throws {
+        // This simulates a login that will sometimes fail.
+        // If it is successful, it just updates the athenticationStatus property with that string
+        // If it fails, it sets authenticationStatus to Try again but also sets the alertString
+        // Published property to a non-optional instance of the AlertString struct and
+        // The errorString property can then be used in your view for your alert Message
+        // The key to this is to use the .alert(item:   ) constructor instead of the .alert(.isPresented: ) one
+        // This one triggers every time an optional property is set (alertString?) and the alert will
+        // then give you that instance of that property from which we can extract the errorString
+        // And use it in the Alert.
+
+        let random = Bool.random()
+            if random {
+                authenticationStatus = "Logged in Successfully"
+            } else {
+                authenticationStatus = "Try again"
+                self.alertString = AlertString(errorString: "Login Failed")
+                throw AuthenticationError.failed
+            }
+    }
+}