Modernize app example (#231)

Since we already required Swift 5.5 for Concurrency (Xcode 13), it's natural to update the demo app to reflect latest SwiftUI changes, which makes the code neater and more expressive.

Author: stevapple

Examples/LocalDebugging/MyApp/MyApp.xcodeproj/project.pbxproj

@@ -2,7 +2,7 @@
 //
 // This source file is part of the SwiftAWSLambdaRuntime open source project
 //
-// Copyright (c) 2020 Apple Inc. and the SwiftAWSLambdaRuntime project authors
+// Copyright (c) 2020-2021 Apple Inc. and the SwiftAWSLambdaRuntime project authors
 // Licensed under Apache License v2.0
 //
 // See LICENSE.txt for license information
@@ -19,30 +19,43 @@ struct ContentView: View {
     @State var name: String = ""
     @State var password: String = ""
     @State var response: String = ""
+    @State private var isLoading: Bool = false
 
     var body: some View {
         VStack(alignment: .leading, spacing: 20) {
             TextField("Username", text: $name)
             SecureField("Password", text: $password)
-            Button(
-                action: {
-                    Task {
-                        await self.register()
+            let inputIncomplete = name.isEmpty || password.isEmpty
+            Button {
+                Task {
+                    isLoading = true
+                    do {
+                        response = try await self.register()
+                    } catch {
+                        response = error.localizedDescription
                     }
-                },
-                label: {
-                    Text("Register")
-                        .padding()
-                        .foregroundColor(.white)
-                        .background(Color.black)
-                        .border(Color.black, width: 2)
+                    isLoading = false
                 }
-            )
+            } label: {
+                Text("Register")
+                    .padding()
+                    .foregroundColor(.white)
+                    .background(.black)
+                    .border(.black, width: 2)
+                    .opacity(isLoading ? 0 : 1)
+                    .overlay {
+                        if isLoading {
+                            ProgressView()
+                        }
+                    }
+            }
+            .disabled(inputIncomplete || isLoading)
+            .opacity(inputIncomplete ? 0.5 : 1)
             Text(response)
         }.padding(100)
     }
 
-    func register() async {
+    func register() async throws -> String {
         guard let url = URL(string: "http://127.0.0.1:7000/invoke") else {
             fatalError("invalid url")
         }
@@ -54,27 +67,17 @@ struct ContentView: View {
         }
         request.httpBody = jsonRequest
 
-        do {
-            let (data, response) = try await URLSession.shared.data(for: request)
-
-            guard let httpResponse = response as? HTTPURLResponse else {
-                throw CommunicationError(reason: "invalid response, expected HTTPURLResponse")
-            }
-            guard httpResponse.statusCode == 200 else {
-                throw CommunicationError(reason: "invalid response code: \(httpResponse.statusCode)")
-            }
-            let jsonResponse = try JSONDecoder().decode(Response.self, from: data)
+        let (data, response) = try await URLSession.shared.data(for: request)
 
-            self.response = jsonResponse.message
-        } catch {
-            self.response = error.localizedDescription
+        guard let httpResponse = response as? HTTPURLResponse else {
+            throw CommunicationError(reason: "Invalid response, expected HTTPURLResponse.")
         }
-    }
-
-    func setResponse(_ text: String) {
-        DispatchQueue.main.async {
-            self.response = text
+        guard httpResponse.statusCode == 200 else {
+            throw CommunicationError(reason: "Invalid response code: \(httpResponse.statusCode)")
         }
+
+        let jsonResponse = try JSONDecoder().decode(Response.self, from: data)
+        return jsonResponse.message
     }
 }
 
@@ -84,6 +87,9 @@ struct ContentView_Previews: PreviewProvider {
     }
 }
 
-struct CommunicationError: Error {
+struct CommunicationError: LocalizedError {
     let reason: String
+    var errorDescription: String? {
+        self.reason
+    }
 }

Examples/LocalDebugging/MyApp/MyApp.xcodeproj/xcshareddata/xcschemes/MyApp.xcscheme

@@ -0,0 +1,24 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the SwiftAWSLambdaRuntime open source project
+//
+// Copyright (c) 2021 Apple Inc. and the SwiftAWSLambdaRuntime project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of SwiftAWSLambdaRuntime project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+import SwiftUI
+
+@main
+struct MyApp: App {
+    var body: some Scene {
+        WindowGroup {
+            ContentView()
+        }
+    }
+}