版本記錄

前言

數(shù)據(jù)的持久化存儲(chǔ)是移動(dòng)端不可避免的一個(gè)問(wèn)題，很多時(shí)候的業(yè)務(wù)邏輯都需要我們進(jìn)行本地化存儲(chǔ)解決和完成，我們可以采用很多持久化存儲(chǔ)方案，比如說(shuō)plist文件（屬性列表）、preference（偏好設(shè)置）、NSKeyedArchiver（歸檔）、SQLite 3、CoreData，這里基本上我們都用過(guò)。這幾種方案各有優(yōu)缺點(diǎn)，其中，CoreData是蘋果極力推薦我們使用的一種方式，我已經(jīng)將它分離出去一個(gè)專題進(jìn)行說(shuō)明講解。這個(gè)專題主要就是針對(duì)另外幾種數(shù)據(jù)持久化存儲(chǔ)方案而設(shè)立。
1. 數(shù)據(jù)持久化方案解析（一） —— 一個(gè)簡(jiǎn)單的基于SQLite持久化方案示例（一）
2. 數(shù)據(jù)持久化方案解析（二） —— 一個(gè)簡(jiǎn)單的基于SQLite持久化方案示例（二）
3. 數(shù)據(jù)持久化方案解析（三） —— 基于NSCoding的持久化存儲(chǔ)（一）
4. 數(shù)據(jù)持久化方案解析（四） —— 基于NSCoding的持久化存儲(chǔ)（二）
5. 數(shù)據(jù)持久化方案解析（五） —— 基于Realm的持久化存儲(chǔ)（一）
6. 數(shù)據(jù)持久化方案解析（六） —— 基于Realm的持久化存儲(chǔ)（二）
7. 數(shù)據(jù)持久化方案解析（七） —— 基于Realm的持久化存儲(chǔ)（三）
8. 數(shù)據(jù)持久化方案解析（八） —— UIDocument的數(shù)據(jù)存儲(chǔ)（一）
9. 數(shù)據(jù)持久化方案解析（九） —— UIDocument的數(shù)據(jù)存儲(chǔ)（二）
10. 數(shù)據(jù)持久化方案解析（十） —— UIDocument的數(shù)據(jù)存儲(chǔ)（三）
11. 數(shù)據(jù)持久化方案解析（十一） —— 基于Core Data 和 SwiftUI的數(shù)據(jù)存儲(chǔ)示例（一）

源碼

1. Swift

首先看下工程組織結(jié)構(gòu)

下面就是源碼了

1. AddMovie.swift

import SwiftUI

struct AddMovie: View {
  static let DefaultMovieTitle = "An untitled masterpiece"
  static let DefaultMovieGenre = "Genre-buster"

  @State var title = ""
  @State var genre = ""
  @State var releaseDate = Date()
  let onComplete: (String, String, Date) -> Void

  var body: some View {
    NavigationView {
      Form {
        Section(header: Text("Title")) {
          TextField("Title", text: $title)
        }
        Section(header: Text("Genre")) {
          TextField("Genre", text: $genre)
        }
        Section {
          DatePicker(
            selection: $releaseDate,
            displayedComponents: .date) {
              Text("Release Date").foregroundColor(Color(.gray))
          }
        }
        Section {
          Button(action: addMoveAction) {
            Text("Add Movie")
          }
        }
      }
      .navigationBarTitle(Text("Add Movie"), displayMode: .inline)
    }
  }

  private func addMoveAction() {
    onComplete(
      title.isEmpty ? AddMovie.DefaultMovieTitle : title,
      genre.isEmpty ? AddMovie.DefaultMovieGenre : genre,
      releaseDate)
  }
}

2. MovieList.swift

import SwiftUI

// swiftlint:disable multiple_closures_with_trailing_closure
struct MovieList: View {
  @Environment(\.managedObjectContext) var managedObjectContext
  // 1.
  @FetchRequest(
    // 2.
    entity: Movie.entity(),
    // 3.
    sortDescriptors: [
      NSSortDescriptor(keyPath: \Movie.title, ascending: true)
    ]
    //,predicate: NSPredicate(format: "genre contains 'Action'")
    // 4.
  ) var movies: FetchedResults<Movie>

  @State var isPresented = false

  var body: some View {
    NavigationView {
      List {
        ForEach(movies, id: \.title) {
          MovieRow(movie: $0)
        }
        .onDelete(perform: deleteMovie)
      }
      .sheet(isPresented: $isPresented) {
        AddMovie { title, genre, release in
          self.addMovie(title: title, genre: genre, releaseDate: release)
          self.isPresented = false
        }
      }
      .navigationBarTitle(Text("Fave Flicks"))
      .navigationBarItems(trailing:
        Button(action: { self.isPresented.toggle() }) {
          Image(systemName: "plus")
        }
      )
    }
  }

  func deleteMovie(at offsets: IndexSet) {
    // 1.
    offsets.forEach { index in
      // 2.
      let movie = self.movies[index]

      // 3.
      self.managedObjectContext.delete(movie)
    }

    // 4.
    saveContext()
  }


  func addMovie(title: String, genre: String, releaseDate: Date) {
    // 1
    let newMovie = Movie(context: managedObjectContext)

    // 2
    newMovie.title = title
    newMovie.genre = genre
    newMovie.releaseDate = releaseDate

    // 3
    saveContext()
  }


  func saveContext() {
    do {
      try managedObjectContext.save()
    } catch {
      print("Error saving managed object context: \(error)")
    }
  }
}

struct MovieList_Previews: PreviewProvider {
  static var previews: some View {
    MovieList()
  }
}

3. MovieRow.swift

import SwiftUI

struct MovieRow: View {
  let movie: Movie
  static let releaseFormatter: DateFormatter = {
    let formatter = DateFormatter()
    formatter.dateStyle = .long
    return formatter
  }()

  var body: some View {
    VStack(alignment: .leading) {
      movie.title.map(Text.init)
        .font(.title)
      HStack {
        movie.genre.map(Text.init)
          .font(.caption)
        Spacer()
        movie.releaseDate.map { Text(Self.releaseFormatter.string(from: $0)) }
          .font(.caption)
      }
    }
  }
}

4. AppDelegate.swift

import SwiftUI

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
  // MARK: UISceneSession Lifecycle

  func application(
    _ application: UIApplication,
    configurationForConnecting connectingSceneSession: UISceneSession,
    options: UIScene.ConnectionOptions
  ) -> UISceneConfiguration {
    return UISceneConfiguration(
      name: "Default Configuration",
      sessionRole: connectingSceneSession.role)
  }
}

5. SceneDelegate.swift

import SwiftUI
import CoreData

class SceneDelegate: UIResponder, UIWindowSceneDelegate {
  var window: UIWindow?

  func scene(
    _ scene: UIScene,
    willConnectTo session: UISceneSession,
    options connectionOptions: UIScene.ConnectionOptions
  ) {
    let context = persistentContainer.viewContext
    let contentView = MovieList().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 sceneDidEnterBackground(_ scene: UIScene) {
    saveContext()
  }

  // MARK: - Core Data stack

  lazy var persistentContainer: NSPersistentContainer = {
    let container = NSPersistentContainer(name: "FaveFlicks")
    container.loadPersistentStores { _, error in
      if let error = error as NSError? {
        // You should add your own error handling code here.
        fatalError("Unresolved error \(error), \(error.userInfo)")
      }
    }
    return container
  }()

  // MARK: - Core Data Saving support

  func saveContext() {
    let context = persistentContainer.viewContext
    if context.hasChanges {
      do {
        try context.save()
      } catch {
        // The context couldn't be saved.
        // You should add your own error handling here.
        let nserror = error as NSError
        fatalError("Unresolved error \(nserror), \(nserror.userInfo)")
      }
    }
  }
}

后記

本篇主要講述了基于Core Data 和 SwiftUI的數(shù)據(jù)存儲(chǔ)示例，感興趣的給個(gè)贊或者關(guān)注~~~