版本记录

版本号	时间
V1.0	2020.11.11 星期三

前言

数据的持久化存储是移动端不可避免的一个问题，很多时候的业务逻辑都需要我们进行本地化存储解决和完成，我们可以采用很多持久化存储方案，比如说plist文件（属性列表）、preference（偏好设置）、NSKeyedArchiver（归档）、SQLite 3、CoreData，这里基本上我们都用过。这几种方案各有优缺点，其中，CoreData是苹果极力推荐我们使用的一种方式，我已经将它分离出去一个专题进行说明讲解。这个专题主要就是针对另外几种数据持久化存储方案而设立。
1. 数据持久化方案解析（一） —— 一个简单的基于SQLite持久化方案示例（一）
2. 数据持久化方案解析（二） —— 一个简单的基于SQLite持久化方案示例（二）
3. 数据持久化方案解析（三） —— 基于NSCoding的持久化存储（一）
4. 数据持久化方案解析（四） —— 基于NSCoding的持久化存储（二）
5. 数据持久化方案解析（五） —— 基于Realm的持久化存储（一）
6. 数据持久化方案解析（六） —— 基于Realm的持久化存储（二）
7. 数据持久化方案解析（七） —— 基于Realm的持久化存储（三）
8. 数据持久化方案解析（八） —— UIDocument的数据存储（一）
9. 数据持久化方案解析（九） —— UIDocument的数据存储（二）
10. 数据持久化方案解析（十） —— UIDocument的数据存储（三）
11. 数据持久化方案解析（十一） —— 基于Core Data 和 SwiftUI的数据存储示例（一）
12. 数据持久化方案解析（十二） —— 基于Core Data 和 SwiftUI的数据存储示例（二）
13. 数据持久化方案解析（十三） —— 基于Unit Testing的Core Data测试（一）
14. 数据持久化方案解析（十四） —— 基于Unit Testing的Core Data测试（二）
15. 数据持久化方案解析（十五） —— 基于Realm和SwiftUI的数据持久化简单示例（一）
16. 数据持久化方案解析（十六） —— 基于Realm和SwiftUI的数据持久化简单示例（二）
17. 数据持久化方案解析（十七） —— 基于NSPersistentCloudKitContainer的Core Data和CloudKit的集成示例（一）

开始

1. Swift

首先看下工程组织目录

下面就是源码了

1. AppDelegate.swift

import UIKit

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate { }

2. SceneDelegate.swift

import UIKit
import SwiftUI

class SceneDelegate: UIResponder, UIWindowSceneDelegate {
    var window: UIWindow?
    private let coreDataStack = CoreDataStack.shared

  func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
        let context = coreDataStack.context
        let contentView = PlacesListView()
            .environment(\.managedObjectContext, context)

        if let windowScene = scene as? UIWindowScene {
            let window = UIWindow(windowScene: windowScene)
            window.rootViewController = UIHostingController(rootView: contentView)
            self.window = window
            window.makeKeyAndVisible()
        }
  }

  func sceneWillResignActive(_ scene: UIScene) {
    coreDataStack.saveContext()
  }
}

3. CoreDataStack.swift

import CoreData

final class CoreDataStack {
  static let shared = CoreDataStack()

  var context: NSManagedObjectContext {
    persistentContainer.viewContext
  }

  private lazy var persistentContainer: NSPersistentCloudKitContainer = {
    let container = NSPersistentCloudKitContainer(name: "PlaceTag")
    migrateIfRequired(container.persistentStoreCoordinator)
    container.persistentStoreDescriptions.first?.url = CoreDataStack.storeURL
    container.loadPersistentStores { _, error in
      if let error = error as NSError? {
        fatalError("Unresolved error \(error), \(error.userInfo)")
      }
    }
    container.viewContext.automaticallyMergesChangesFromParent = true
    return container
  }()

func migrateIfRequired(_ psc: NSPersistentStoreCoordinator) {
  if FileManager.default.fileExists(atPath: CoreDataStack.storeURL.path) {
    return
  }

  do {
    let store = try psc.addPersistentStore(
      ofType: NSSQLiteStoreType,
      configurationName: nil,
      at: CoreDataStack.storeURL,
      options: CoreDataStack.storeOptions)
    let newStore = try psc.migratePersistentStore(
      store,
      to: CoreDataStack.storeURL,
      options: [NSPersistentStoreRemoveUbiquitousMetadataOption: true],
      withType: NSSQLiteStoreType)
    try psc.remove(newStore)
  } catch {
    print("Error migrating store: \(error)")
  }
}

  private static let storeOptions: [AnyHashable: Any] = [
    NSMigratePersistentStoresAutomaticallyOption: true,
    NSInferMappingModelAutomaticallyOption: true,
    NSPersistentStoreUbiquitousContentNameKey: "CloudStore"
  ]

  private static var storeURL: URL {
    let urls = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)
    guard let docURL = urls.last else {
      fatalError("Error fetching document directory")
    }
    let storeURL = docURL.appendingPathComponent("PlaceTag.sqlite")
    return storeURL
  }

  func saveContext() {
        context.saveContext()
    }
}

4. Place+Extension.swift

import UIKit.UIImage
import CoreData.NSManagedObjectContext

extension Place {
    static func create(title: String?, note: String?, image: UIImage?, context: NSManagedObjectContext) {
        let newPlace = Place(context: context)
        newPlace.id = UUID()
        newPlace.title = title?.isEmpty == false ? title : "Untitled"
        newPlace.note = note?.isEmpty == false ? note : nil
        newPlace.image = image?.pngData()
        newPlace.date = Date()
        context.saveContext()
    }
}

5. NSManagedObjectContext+Extension.swift

import CoreData

extension NSManagedObjectContext {
    func saveContext() {
        do {
            try save()
        } catch {
            let nserror = error as NSError
            fatalError("Unresolved error \(nserror), \(nserror.userInfo)")
        }
    }

    func delete(_ places: [Place]) {
        let request = NSFetchRequest<NSFetchRequestResult>(entityName: "Place")
        request.predicate = NSPredicate(format: "id IN %@", places.map { $0.id?.uuidString })
        do {
            let results = (try fetch(request) as? [Place]) ?? []
            results.forEach { delete($0) }
        } catch {
            print("Failed removing provided objects")
            return
        }
        saveContext()
    }
}

6. Data+Extension.swift

import UIKit.UIImage

extension Data {
    var uiImage: UIImage? {
        return UIImage(data: self)
    }
}

7. ImagePicker.swift

import SwiftUI

struct ImagePicker: UIViewControllerRepresentable {
    class Coordinator: NSObject, UINavigationControllerDelegate, UIImagePickerControllerDelegate {
        let parent: ImagePicker
        init(_ parent: ImagePicker) {
            self.parent = parent
        }

        func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [UIImagePickerController.InfoKey: Any]) {
            if let uiImage = info[.originalImage] as? UIImage {
                parent.image = uiImage
            }
            parent.presentationMode.wrappedValue.dismiss()
        }
    }
  @Environment(\.presentationMode) var presentationMode
  @Binding var image: UIImage?

    func makeCoordinator() -> Coordinator {
        return Coordinator(self)
    }

    func makeUIViewController(context: UIViewControllerRepresentableContext<ImagePicker>) -> UIImagePickerController {
        let picker = UIImagePickerController()
        picker.delegate = context.coordinator
        return picker
    }

    func updateUIViewController(_ uiViewController: UIImagePickerController, context: UIViewControllerRepresentableContext<ImagePicker>) {
    }
}

8. ActionButtonBackgroundStyle.swift

import SwiftUI

struct ActionButtonBackgroundStyle: ButtonStyle {
    func makeBody(configuration: Self.Configuration) -> some View {
        configuration.label
            .padding()
            .foregroundColor(.white)
            .background(Color.accentColor)
            .clipShape(Capsule())
            .padding([.horizontal])
            .shadow(radius: configuration.isPressed ? 2.0 : 6.0)
            .scaleEffect(configuration.isPressed ? 0.95 : 1)
    }
}

9. AddPlaceView.swift

import SwiftUI

struct AddPlaceView: View {
    @State private var title: String = ""
    @State private var note: String = ""
    @State private var image: UIImage?
    @State private var shouldShowImagePicker = false

    @Environment(\.managedObjectContext) private var viewContext
    @Environment(\.presentationMode) private var presentationMode

    var body: some View {
        ZStack(alignment: .bottomTrailing) {
            Form {
                Section(header: Text("Title")) {
                    TextField("Insert place title here", text: $title)
                        .autocapitalization(.words)
                }

                Section(header: Text("Notes")) {
                    TextField("Insert notes about the place here", text: $note)
                        .autocapitalization(.sentences)
                }

                Section {
                    Button(
                        action: {
                            shouldShowImagePicker.toggle()
                        },
                        label: makeImageForChoosePhotosButton
                    )
                }
            }

            Button(
                action: {
                    Place.create(title: title, note: note, image: image, context: viewContext)
                    presentationMode.wrappedValue.dismiss()
                },
                label: {
                    HStack {
                        Image(systemName: "square.and.arrow.down.fill")
                        Text("Save Place")
                    }
                }
            )
            .buttonStyle(ActionButtonBackgroundStyle())
        }
        .navigationBarTitle("Add Place")
        .sheet(isPresented: $shouldShowImagePicker) {
            ImagePicker(image: $image)
        }
    }

    @ViewBuilder
  private func makeImageForChoosePhotosButton() -> some View {
        image.map {
            Image(uiImage: $0)
                .renderingMode(.original)
                .resizable()
                .aspectRatio(contentMode: .fill)
        }

        if image == nil {
            HStack {
                Spacer()
                Image(systemName: "photo.on.rectangle")
                Text("Choose Photo")
                Spacer()
            }
            .frame(minWidth: 0, maxWidth: .infinity, minHeight: 0, maxHeight: .infinity)
        }
    }
}

struct AddPlaceView_Previews: PreviewProvider {
    static var previews: some View {
        AddPlaceView()
    }
}

10. PlacesListView.swift

import SwiftUI
import CoreData

struct PlacesListView: View {
    @FetchRequest(entity: Place.entity(), sortDescriptors: [NSSortDescriptor(keyPath: \Place.date, ascending: false)])
    private var places: FetchedResults<Place>
    @Environment(\.managedObjectContext) private var viewContext

    var body: some View {
        NavigationView {
            ZStack(alignment: .bottomTrailing) {
                List {
                    ForEach(places, id: \.id) { place in
                        NavigationLink(destination: makeDetailView(from: place)) {
                            makeItemView(from: place)
                        }
                    }.onDelete(perform: deletePlaces)
                }
                .listStyle(GroupedListStyle())
                .overlay(places.isEmpty ? Text("Add a place using the button below") : nil, alignment: .center)

                NavigationLink(destination: AddPlaceView()) {
                    HStack {
                        Image(systemName: "plus.circle.fill")
                        Text("Add Place")
                    }
                }
                .buttonStyle(ActionButtonBackgroundStyle())
            }
            .navigationBarTitle("PlaceTag")
        }
    }

    private func makeDetailView(from place: Place) -> PlaceDetailView {
        return PlaceDetailView(
            title: place.title,
            subtitle: place.note,
            image: place.image?.uiImage)
    }

    private func makeItemView(from place: Place) -> PlaceItemView {
        return PlaceItemView(
            title: place.title,
            subtitle: place.note,
            image: place.image?.uiImage
        )
    }

    private func deletePlaces(at indices: IndexSet) {
        DispatchQueue.main.async {
      var result: [Place] = []
            for index in indices {
                result.append(places[index])
            }
            viewContext.delete(result)
        }
    }
}

11. PlaceItemView.swift

import SwiftUI

struct PlaceItemView: View {
    let title: String?
    let subtitle: String?
    let image: UIImage?

    var body: some View {
        HStack(spacing: 16) {
            image.map {
                Image(uiImage: $0)
                    .renderingMode(.original)
                    .resizable()
                    .aspectRatio(contentMode: .fill)
                    .frame(width: 80, height: 80)
                    .cornerRadius(4)
                    .padding(.vertical)
            }

            VStack(alignment: .leading) {
                title.map {
                    Text($0)
                        .font(.headline)
                }
                subtitle.map {
                    Text($0)
                        .font(.subheadline)
                }
            }
        }
    }
}

struct PlaceItemView_Previews: PreviewProvider {
    static var previews: some View {
        PlaceItemView(
            title: "San Francisco",
            subtitle: "Golden gate was awesome",
            image: UIImage(systemName: "photo")
        )
    }
}

12. PlaceDetailView.swift

import SwiftUI

struct PlaceDetailView: View {
    let title: String?
    let subtitle: String?
    let image: UIImage?

    var body: some View {
        ScrollView {
            VStack {
                image.map {
                    Image(uiImage: $0)
                        .renderingMode(.original)
                        .resizable()
                        .aspectRatio(contentMode: .fit)
                        .cornerRadius(8)
                        .shadow(radius: 10)
                }
                title.map {
                    Text($0)
                        .font(.largeTitle)
                }
                subtitle.map {
                    Text($0)
                        .font(.title)
                        .foregroundColor(.secondary)
                }
            }
            .multilineTextAlignment(.center)
            .padding()
        }
        .navigationBarTitle(Text(""), displayMode: .inline)
    }
}

struct PlaceDetailView_Previews: PreviewProvider {
    static var previews: some View {
        PlaceDetailView(
            title: "San Francisco",
            subtitle: "Golden Gate was awesome",
            image: UIImage(systemName: "photo")
        )
    }
}

后记

本篇主要讲述了基于NSPersistentCloudKitContainer的Core Data和CloudKit的集成示例，感兴趣的给个赞或者关注~~~