Part 8: A Quick and Dirty App UI

AppShared/ContentView.swift

@@ -9,22 +9,11 @@ import SwiftUI
 
 struct ContentView: View {
     var body: some View {
-        VStack {
+        #if os(iOS) // iOS can add and remove
-            Image(systemName: "globe")
+            ListOfThingsView()
-                .imageScale(.large)
+        #elseif os(tvOS) || os(watchOS) ||  os(macOS) // macOS and tvOS and watchOS just show a readonly list
-                .foregroundColor(.accentColor)
+            SimpleListOfThingsView()
-
+        #endif
-            #if os(iOS)
-            Text("Hello \(UIDevice.isIPad ? "iPadOS" : "iOS")")
-            #elseif os(macOS)
-            Text("Hello macOS")
-            #elseif os(tvOS)
-            Text("Hello tvOS")
-            #elseif os(watchOS)
-            Text("Hello watchOS")
-            #endif
-        }
-        .padding()
     }
 }
 

AppShared/JustOneThingApp.swift

@@ -9,10 +9,11 @@ import SwiftUI
 
 @main
 struct JustOneThingApp: App {
-    let persistenceController = PersistenceController.shared
+    let persistenceController = PersistenceController.preview // or PersistenceController.shared
     var body: some Scene {
         WindowGroup {
             ContentView()
+                .environment(\.managedObjectContext, persistenceController.container.viewContext)
         }
     }
 }

AppShared/SimpleListOfThingsView.swift

@@ -0,0 +1,25 @@
+//
+//  SimpleListOfThingsView.swift
+//  JustOneThingWatch
+//
+//  Created by Alan Francis on 10/07/2023.
+//
+
+import SwiftUI
+import CoreData
+
+struct SimpleListOfThingsView: View {
+    @Environment(\.managedObjectContext) private var viewContext
+    @FetchRequest(
+        sortDescriptors: [NSSortDescriptor(keyPath: \PersistentThing.createdAt, ascending: true)],
+        animation: .default)
+    private var items: FetchedResults<PersistentThing>
+    
+    var body: some View {
+        List {
+            ForEach(items) { item in
+                Text(item.text ?? "no text")
+            }
+        }
+    }
+}

JustOneThing.xcodeproj/project.pbxproj

@@ -7,6 +7,9 @@
 	objects = {
 
 /* Begin PBXBuildFile section */
+		5405B2992A5C939C00B36DB6 /* ListOfThingsView.swift in Sources */ = {isa = PBXBuildFile; fileRef = 5405B2982A5C939C00B36DB6 /* ListOfThingsView.swift */; };
+		5405B29B2A5C94BA00B36DB6 /* SimpleListOfThingsView.swift in Sources */ = {isa = PBXBuildFile; fileRef = 5405B29A2A5C94BA00B36DB6 /* SimpleListOfThingsView.swift */; };
+		5405B2BC2A5CA1A700B36DB6 /* SimpleListOfThingsView.swift in Sources */ = {isa = PBXBuildFile; fileRef = 5405B29A2A5C94BA00B36DB6 /* SimpleListOfThingsView.swift */; };
 		5407E5022A2A8AE200EF00B8 /* JustOneThingApp.swift in Sources */ = {isa = PBXBuildFile; fileRef = 5483903A2A2A773900BF5624 /* JustOneThingApp.swift */; };
 		5407E5032A2A8AE700EF00B8 /* ContentView.swift in Sources */ = {isa = PBXBuildFile; fileRef = 5483903C2A2A773900BF5624 /* ContentView.swift */; };
 		5407E5042A2A8AEA00EF00B8 /* Assets.xcassets in Resources */ = {isa = PBXBuildFile; fileRef = 5483903E2A2A773A00BF5624 /* Assets.xcassets */; };
@@ -131,6 +134,8 @@
 /* End PBXCopyFilesBuildPhase section */
 
 /* Begin PBXFileReference section */
+		5405B2982A5C939C00B36DB6 /* ListOfThingsView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ListOfThingsView.swift; sourceTree = "<group>"; };
+		5405B29A2A5C94BA00B36DB6 /* SimpleListOfThingsView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = SimpleListOfThingsView.swift; sourceTree = "<group>"; };
 		5407E5062A35B96E00EF00B8 /* JustOneThingWatch.entitlements */ = {isa = PBXFileReference; lastKnownFileType = text.plist.entitlements; path = JustOneThingWatch.entitlements; sourceTree = "<group>"; };
 		5416C7372A56A867002196EE /* InterfaceExtensions.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = InterfaceExtensions.swift; sourceTree = "<group>"; };
 		5431ED6D2A2A77C900515680 /* JustOneThingWatch.app */ = {isa = PBXFileReference; explicitFileType = wrapper.application; includeInIndex = 0; path = JustOneThingWatch.app; sourceTree = BUILT_PRODUCTS_DIR; };
@@ -212,6 +217,7 @@
 			children = (
 				5483903A2A2A773900BF5624 /* JustOneThingApp.swift */,
 				5483903C2A2A773900BF5624 /* ContentView.swift */,
+				5405B29A2A5C94BA00B36DB6 /* SimpleListOfThingsView.swift */,
 				5483903E2A2A773A00BF5624 /* Assets.xcassets */,
 			);
 			path = AppShared;
@@ -271,6 +277,7 @@
 			children = (
 				5432A6032A582D5D00FE2351 /* Info.plist */,
 				548390402A2A773A00BF5624 /* JustOneThing.entitlements */,
+				5405B2982A5C939C00B36DB6 /* ListOfThingsView.swift */,
 			);
 			path = JustOneThing;
 			sourceTree = "<group>";
@@ -532,6 +539,7 @@
 			files = (
 				5407E5032A2A8AE700EF00B8 /* ContentView.swift in Sources */,
 				54AE28422A5823D900719A56 /* JustOneThingCloudModel.xcdatamodeld in Sources */,
+				5405B2BC2A5CA1A700B36DB6 /* SimpleListOfThingsView.swift in Sources */,
 				5407E5022A2A8AE200EF00B8 /* JustOneThingApp.swift in Sources */,
 				547201932A365868005B2FCC /* Widget.intentdefinition in Sources */,
 				54AE28482A58245700719A56 /* PersistenceController.swift in Sources */,
@@ -544,7 +552,9 @@
 			files = (
 				5483903D2A2A773900BF5624 /* ContentView.swift in Sources */,
 				54AE28412A5823D900719A56 /* JustOneThingCloudModel.xcdatamodeld in Sources */,
+				5405B2992A5C939C00B36DB6 /* ListOfThingsView.swift in Sources */,
 				5483903B2A2A773900BF5624 /* JustOneThingApp.swift in Sources */,
+				5405B29B2A5C94BA00B36DB6 /* SimpleListOfThingsView.swift in Sources */,
 				54928C222A35F89A00095445 /* Widget.intentdefinition in Sources */,
 				54AE28472A58245700719A56 /* PersistenceController.swift in Sources */,
 			);

JustOneThing/ListOfThingsView.swift

@@ -0,0 +1,85 @@
+//
+//  ListOfThingsView.swift
+//  JustOneThing
+//
+//  Created by Alan Francis on 10/07/2023.
+//
+
+import SwiftUI
+import CoreData
+
+struct ListOfThingsView: View {
+    @Environment(\.managedObjectContext) private var viewContext
+
+    @FetchRequest(
+        sortDescriptors: [NSSortDescriptor(keyPath: \PersistentThing.createdAt, ascending: true)],
+        animation: .default)
+    private var things: FetchedResults<PersistentThing>
+    private let timeFormatter: DateFormatter = {
+        let formatter = DateFormatter()
+        formatter.dateStyle = .none
+        formatter.timeStyle = .medium
+        return formatter
+    }()
+
+    var body: some View {
+        NavigationView {
+            List {
+                ForEach(things) { thing in
+                    NavigationLink {
+                        Text(thing.text ?? "no text")
+                    } label: {
+                        Text(thing.text ?? "no text")
+                    }
+                }
+                .onDelete(perform: deleteItems)
+            }
+            #if os(iOS)
+                .toolbar {
+                    ToolbarItem(placement: .navigationBarTrailing) {
+                        EditButton()
+                    }
+                    ToolbarItem {
+                        Button(action: addItem) {
+                            Label("Add Item", systemImage: "plus")
+                        }
+                    }
+                }
+            #endif
+            Text("Select an item")
+        }
+    }
+
+    private func addItem() {
+        withAnimation {
+            let newThing = PersistentThing(context: viewContext)
+            newThing.createdAt = Date()
+            newThing.uuid = UUID()
+            newThing.text = "thing created \(timeFormatter.string(from: Date()))"
+
+            do {
+                try viewContext.save()
+            } catch {
+                // Replace this implementation with code to handle the error appropriately.
+                // fatalError() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
+                let nsError = error as NSError
+                fatalError("Unresolved error \(nsError), \(nsError.userInfo)")
+            }
+        }
+    }
+
+    private func deleteItems(offsets: IndexSet) {
+        withAnimation {
+            offsets.map { things[$0] }.forEach(viewContext.delete)
+
+            do {
+                try viewContext.save()
+            } catch {
+                // Replace this implementation with code to handle the error appropriately.
+                // fatalError() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
+                let nsError = error as NSError
+                fatalError("Unresolved error \(nsError), \(nsError.userInfo)")
+            }
+        }
+    }
+}

Model/PersistenceController.swift

@@ -84,4 +84,26 @@ extension PersistenceController {
 }
 
 
-
+extension PersistenceController {
+    static var preview: PersistenceController = {
+        let result = PersistenceController(inMemory: true)
+        let viewContext = result.container.viewContext
+        var i = 1
+        for _ in 0..<10 {
+            let newItem = PersistentThing(context: viewContext)
+            newItem.text = "action \(i)"
+            newItem.createdAt = Date()
+            newItem.uuid = UUID()
+            i = i+1
+        }
+        do {
+            try viewContext.save()
+        } catch {
+            // Replace this implementation with code to handle the error appropriately.
+            // fatalError() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
+            let nsError = error as NSError
+            fatalError("Unresolved error \(nsError), \(nsError.userInfo)")
+        }
+        return result
+    }()
+}