【Swift5】メモ：既存のプロジェクトにCoreDataを追加する

はじめに

アプリ作成時に「Use Core Data」にチェックをつければ自動でこれらが追加されますが、後から使いたくなった時は少し面倒だったので、コピペで使えるようにまとめておきます。

AppDelegate.swift

import CoreData

iCloudにデータを保管できるようにする場合は NSPersistentCloudKitContainer、そうでない場合はNSPersistentContainerを使います。

// MARK: - Core Data stack

lazy var persistentContainer: NSPersistentCloudKitContainer = {
    /*
    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 = NSPersistentCloudKitContainer(name: "coredataSample")
    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
}()

// MARK: - Core Data Saving support

func saveContext () {
    let context = persistentContainer.viewContext
        if context.hasChanges {
            do {
                try context.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)")
            }
      }
}