CloudCore

CloudCore is a framework that manages syncing between iCloud (CloudKit) and Core Data written on native Swift. It maybe used are CloudKit caching.

Features

• Sync manually or on push notifications.
• Differential sync, only changed object and values are uploaded and downloaded. CloudCore even differs changed and not changed values inside objects.
• Respects of Core Data options (cascade deletions, external storage).
• Knows and manages with CloudKit errors like userDeletedZone, zoneNotFound, changeTokenExpired, isMore.
• Covered with Unit and CloudKit online tests.
• All public methods are 100% documented.
• Currently only private database is supported.

How it works?

CloudCore is built using black box architecture, so it works invisibly for your application, you just need to add several lines to AppDelegate to enable it. Synchronization and error resolving is managed automatically.

1. CloudCore stores change tokens from CloudKit, so only changed data is downloaded.
2. When CloudCore is enabled (CloudCore.enable) it fetches changed data from CloudKit and subscribes to CloudKit push notifications about new changes.
3. When CloudCore.fetchAndSave is called manually or by push notification, CloudCore fetches and saves changed data to Core Data.
4. When data is written to persistent container (parent context is saved) CloudCore founds locally changed data and uploads it to CloudKit.

Installation

CocoaPods

CloudCore is available through CocoaPods. To install it, simply add the following line to your Podfile:

pod 'CloudCore', '~> 2.0'

How to help?

Current version of framework hasn’t been deeply tested and may contain errors. If you can test framework, I will be very glad. If you found an error, please post an issue.

Documentation

All public methods are documented using XCode Markup and available inside XCode. HTML-generated version of that documentation is available here.

Quick start

1. Enable CloudKit capability for you application:

2. Add 2 service attributes to each entity in CoreData model you want to sync:

   • recordData attribute with Binary type
   • recordID attribute with String type

3. Make changes in your AppDelegate.swift file:

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
  // Register for push notifications about changes
  application.registerForRemoteNotifications()

  // Enable CloudCore syncing
  CloudCore.enable(persistentContainer: persistentContainer, errorDelegate: self)

  return true
}

// Notification from CloudKit about changes in remote database
func application(_ application: UIApplication, didReceiveRemoteNotification userInfo: [AnyHashable : Any], fetchCompletionHandler completionHandler: @escaping (UIBackgroundFetchResult) -> Void) {
  // Check if it CloudKit's and CloudCore notification
  if CloudCore.isCloudCoreNotification(withUserInfo: userInfo) {
    // Fetch changed data from iCloud
    CloudCore.fetchAndSave(using: userInfo, to: persistentContainer, error: nil, completion: { (fetchResult) in
      completionHandler(fetchResult.uiBackgroundFetchResult)
    })
  }
}

func applicationWillTerminate(_ application: UIApplication) {
    // Save tokens on exit used to differential sync
    CloudCore.tokens.saveToUserDefaults()
}

1. Make first run of your application in a development environment, fill an example data in Core Data and wait until sync completes. CloudCore create needed CloudKit schemes automatically.

Service attributes

CloudCore stores service CloudKit information in managed objects, you need to add that attributes to your Core Data model. If required attributes are not found in entity that entity won’t be synced.

Required attributes for each synced entity:

1. Record Data attribute with Binary type
2. Record ID attribute with String type

You may specify attributes’ names in 2 ways (you may combine that ways in different entities).

User Info

First off CloudCore try to search attributes by looking up User Info at your model, you may specify User Info key CloudCoreType fro attribute to mark one as service one. Values are:

• Record Data value is recordData.
• Record ID value is recordID.

Default names

The most simple way is to name attributes with default names because you don’t need to specify any User Info.

💡 Tips

• You can name attribute as you want, value of User Info is not changed (you can create attribute myid with User Info: CloudCoreType: recordID)
• I recommend to mark Record ID attribute as Indexed, that can speed up updates in big databases.
• Record Data attribute is used to store archived version of CKRecord with system fields only (like timestamps, tokens), so don’t worry about size, no real data will be stored here.

Example application

You can find example application at Example directory.

How to run it:

1. Set Bundle Identifier.
2. Check that embedded binaries has a correct path (you can remove and add again CloudCore.framework).
3. If you’re using simulator, login at iCloud on it.

How to use it:

• + button adds new object to local storage (that will be automatically synced to Cloud)
• refresh button calls fetchAndSave to fetch data from Cloud. That is useful button for simulators because Simulator unable to receive push notifications
• Use CloudKit dashboard to make changes and see it at application, and make change in application and see ones in dashboard. Don’t forget to refresh dashboard’s page because it doesn’t update data on-the-fly.

Tests

CloudKit objects can’t be mocked up, that’s why I create 2 different types of tests:

• Tests/Unit here I placed tests that can be performed without CloudKit connection. That tests are executed when you submit a Pull Request.
• Tests/CloudKit here located manual tests, they are most important tests that can be run only in configured environment because they work with CloudKit and your Apple ID.

Nothing will be wrong with your account, tests use only private CKDatabase for application.

Please run these tests before opening pull requests. To run them you need to:

1. Change TestableApp bundle id.
2. Run in simulator or real device TestableApp target.
3. Configure iCloud on that device: Settings.app → iCloud → Login.
4. Run CloudKitTests, they are attached to TestableApp, so CloudKit connection will work.

Roadmap

• [x] Move from alpha to beta status.
• [ ] Add CloudCore.disable method
• [ ] Add methods to clear local cache and remote database
• [ ] Add error resolving for limitExceeded error (split saves by relationships).

Author

Open for hire / relocation. Vasily Ulianov, va…@me.com