Core Dataを試す



> xcodebuild -version
Xcode 13.1
Build version 13A1030d

Core Data とは

Persist or cache data on a single device, or sync data to multiple devices with CloudKit.

  • 単一デバイスにおけるデータ永続化
  • CloudKit を使った複数デバイス間のデータ同期


Entities, Attributes の定義の追加

~.xcdatamodeldGUI 上で設定。

Xcode の Utility Area で確認できる Codegen はデフォルトの Class Definition。


class SceneDelegate: UIResponder, UIWindowSceneDelegate {

    func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
        // Use this method to optionally configure and attach the UIWindow `window` to the provided UIWindowScene `scene`.
        // If using a storyboard, the `window` property will automatically be initialized and attached to the scene.
        // This delegate does not imply the connecting scene or session are new (see `application:configurationForConnectingSceneSession` instead).
        guard let _ = (scene as? UIWindowScene) else { return }
        if let rootVC = window?.rootViewController as? ViewController {
            rootVC.container = persistentContainer


    // MARK: - Core Data stack
    lazy var persistentContainer: NSPersistentContainer = {
         The persistent container for the application. This implementation
         creates and returns a container, having loaded the store for the
         application to it. This property is optional since there are legitimate
         error conditions that could cause the creation of the store to fail.
        let container = NSPersistentContainer(name: "Test20220329_coredata")
        container.loadPersistentStores(completionHandler: { (storeDescription, error) in
            if let error = error as NSError? {
                // 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.
                 Typical reasons for an error here include:
                 * The parent directory does not exist, cannot be created, or disallows writing.
                 * The persistent store is not accessible, due to permissions or data protection when the device is locked.
                 * The device is out of space.
                 * The store could not be migrated to the current model version.
                 Check the error message to determine what the actual problem was.
                fatalError("Unresolved error \(error), \(error.userInfo)")
        return container

Setting Up a Core Data Stack には AppDelegate での初期化が紹介されているが、iOS13以上だとwindowが無くてエラーになる。
iOS13以上では AppDelegate ではなく、SceneDelegate でやるのがスムーズらしい。*1

final class ViewController: UIViewController {
    var container: NSPersistentContainer!
    override func viewDidLoad() {
        guard container != nil else {
            fatalError("This view needs a persistent container.")
        // 保存
        let context = container.viewContext
        let idol = NSEntityDescription.insertNewObject(forEntityName: "Idol", into: context) as! Idol = "櫻木 真乃"
        idol.height = 155

        // 取得
        // let context = container.viewContext
        // let request = NSFetchRequest<NSFetchRequestResult>(entityName: "Idol")
        // let idols = try! context.fetch(request) as! [Idol]
        // for idol in idols {
        //     print(, idol.height)  // Optional("櫻木 真乃") 155
        // }


*1:Apple Developer Forumで質問したらすぐ返ってきた。感謝。