如何为现有Xcode 9 Swift 4 iOS 11项目添加Core Data并适配iCloud？

Got it, let’s walk through adding iCloud + Core Data to your existing project—since you didn’t check the "Use Core Data" box when you started, we’ll build everything from scratch, and make sure it’s compatible with iOS 9 and later, including integrating NSFileCoordinator and NSFilePresenter as needed.

1. Set Up Core Data Manually #

First, we need to lay the groundwork for Core Data in your project:

• Create a new Data Model file (File > New > File > Core Data > Data Model) and define your entities as needed. Name it something like AppDataModel.
• Add a singleton manager class to handle the Core Data stack. Here’s a clean starting template:

  import CoreData
  
  class CoreDataManager {
      static let shared = CoreDataManager()
      
      private init() {}
      
      lazy var persistentContainer: NSPersistentContainer = {
          let container = NSPersistentContainer(name: "AppDataModel")
          // We’ll hook up iCloud config here later
          container.loadPersistentStores(completionHandler: { (storeDescription, error) in
              if let error = error as NSError? {
                  fatalError("Unresolved Core Data error: \(error), \(error.userInfo)")
              }
          })
          return container
      }()
      
      func saveContext() {
          let context = persistentContainer.viewContext
          guard context.hasChanges else { return }
          do {
              try context.save()
          } catch {
              let nserror = error as NSError
              fatalError("Failed to save context: \(nserror), \(nserror.userInfo)")
          }
      }
  }
  

2. Enable iCloud Capabilities #

Next, turn on iCloud for your project:

• Go to your project target > Signing & Capabilities > Click the "+ Capability" button > Add "iCloud".
• Check the CloudKit box (this is the recommended sync method for iOS 9+).
• Under "Containers", add a new container (use the format iCloud.com.yourcompany.yourappname—make sure you remember this identifier for later).

3. Configure Core Data for iCloud Sync #

Now we’ll update the Core Data stack to talk to iCloud. Note that NSPersistentCloudKitContainer (a subclass of NSPersistentContainer) simplifies this for iOS 10+, but we’ll include a fallback for iOS 9:

For iOS 10+ (Recommended) #

Update the persistentContainer property in your CoreDataManager:

lazy var persistentContainer: NSPersistentCloudKitContainer = {
    let container = NSPersistentCloudKitContainer(name: "AppDataModel")
    
    guard let storeDescription = container.persistentStoreDescriptions.first else {
        fatalError("No persistent store description found")
    }
    
    // Enable history tracking and remote change notifications
    storeDescription.setOption(true as NSNumber, forKey: NSPersistentHistoryTrackingKey)
    storeDescription.setOption(true as NSNumber, forKey: NSPersistentStoreRemoteChangeNotificationPostOptionKey)
    
    // Link to your iCloud container
    storeDescription.cloudKitContainerOptions = NSPersistentCloudKitContainerOptions(containerIdentifier: "iCloud.com.yourcompany.yourappname")
    
    container.loadPersistentStores(completionHandler: { (storeDescription, error) in
        if let error = error as NSError? {
            fatalError("Unresolved Core Data error: \(error), \(error.userInfo)")
        }
    })
    
    // Auto-merge iCloud changes into the view context
    container.viewContext.automaticallyMergesChangesFromParent = true
    container.viewContext.mergePolicy = NSMergeByPropertyObjectTrumpMergePolicy
    
    return container
}()

For iOS 9 Compatibility #

If you need to support iOS 9, replace the CloudKit setup with the older iCloud Core Data options:

// Inside the persistentContainer setup
storeDescription.setOption("iCloud.com.yourcompany.yourappname" as NSString, forKey: NSPersistentStoreUbiquitousContentNameKey)
storeDescription.setOption(FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first! as NSURL, forKey: NSPersistentStoreUbiquitousContentURLKey)

You’ll also need to listen for NSPersistentStoreDidImportUbiquitousContentChangesNotification and manually merge changes into your context.

4. Integrate NSFileCoordinator & NSFilePresenter #

These components are critical for avoiding file access conflicts when syncing with iCloud—they ensure your app and the iCloud daemon don’t modify the Core Data store file at the same time.

Implement NSFilePresenter #

Create a class to monitor changes to your Core Data store:

class CoreDataFilePresenter: NSObject, NSFilePresenter {
    var presentedItemURL: URL?
    let presentedItemOperationQueue = OperationQueue.main
    
    private let coreDataManager: CoreDataManager
    
    init(coreDataManager: CoreDataManager) {
        self.coreDataManager = coreDataManager
        // Grab the URL of your Core Data store file
        if let storeURL = coreDataManager.persistentContainer.persistentStoreDescriptions.first?.url {
            self.presentedItemURL = storeURL
        }
        super.init()
        NSFileCoordinator.addFilePresenter(self)
    }
    
    // Triggered when iCloud updates the store file
    func presentedItemDidChange() {
        DispatchQueue.main.async {
            self.coreDataManager.persistentContainer.viewContext.refreshAllObjects()
        }
    }
    
    deinit {
        NSFileCoordinator.removeFilePresenter(self)
    }
}

Initialize this presenter in your CoreDataManager’s init() method to start monitoring.

Use NSFileCoordinator for Safe Store Access #

Wrap any direct file operations on your Core Data store (like backups or migrations) in NSFileCoordinator:

func backupCoreDataStore() {
    guard let storeURL = CoreDataManager.shared.persistentContainer.persistentStoreDescriptions.first?.url else { return }
    
    let coordinator = NSFileCoordinator(filePresenter: nil)
    coordinator.coordinate(writingItemAt: storeURL, options: .forReplacing, error: nil) { safeURL in
        let backupURL = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first?.appendingPathComponent("StoreBackup.sqlite")
        try? FileManager.default.copyItem(at: safeURL, to: backupURL!)
    }
}

5. Test the Sync #

• Use a real device (iCloud sync behaves unpredictably on simulators for some scenarios).
• Sign in with an Apple ID that has iCloud enabled.
• Make changes in your app, wait a few seconds, and verify they sync to another device running the same build.

内容的提问来源于stack exchange，提问作者ehounder