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Seamless CloudKit Sync with CoreData
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Pod Version Carthage Compatible Platform License

Seam allows you to sync your CoreData Stores with CloudKit.



  • Automatic mapping of CoreData Models to CloudKit Private Databases
  • Supports Assets
  • Background Sync
  • Conflict Resolution


  • iOS 8.0+ / Mac OS X 10.10+
  • Xcode 7.1+


Please read the Contributing Guidelines before doing any of above.



CocoaPods is a dependency manager for Cocoa projects. You can install it with the following command:

$ gem install cocoapods

To integrate Seam into your Xcode project using CocoaPods, specify it in your Podfile:

source ''
platform :ios, '8.0'

pod 'Seam', '~> 0.6'

Then, run the following command:

$ pod install


Carthage is a decentralized dependency manager that builds your dependencies and provides you with binary frameworks.

You can install Carthage with Homebrew using the following command:

$ brew update
$ brew install carthage

To integrate Seam into your Xcode project using Carthage, specify it in your Cartfile:

github "Seam/Seam" ~> 0.6

Run carthage update to build the framework and drag the built Seam.framework into your Xcode project.


Add a Store type of SeamStoreType to a NSPersistentStoreCoordinator in your CoreData stack:

let persistentStoreCoordinator = NSPersistentStoreCoordinator(managedObjectModel: yourModel)
let seamStore = try persistentStoreCoordinator.addPersistentStoreWithType(SeamStoreType, 
                                                                          configuration: nil, 
                                                                          URL: url, options: nil) as? Store

Observe the following two Notifications to know when the Sync Operation starts and finishes:

NSNotificationCenter.defaultCenter().addObserver(self, selector: "didStartSyncing:",
                                                name: SMStoreDidStartSyncingNotification,
                                                object: seamStore)

NSNotificationCenter.defaultCenter().addObserver(self, selector: "didFinishSyncing:",
                                                name: SMStoreDidFinishSyncingNotification,
                                                object: seamStore)                                               

func didStartSyncing(notification: NSNotification) {
  // Prepare for new data before syncing completes
func didFinishSyncing(notification: NSNotification) {
  // Merge Changes into your context after syncing completes

Finally call sync whenever and wherever you want:


To trigger sync whenever a change happens on the CloudKit Servers. Subscribe the store to receive Push Notifications from the CloudKit Servers.

seamStore.subscribeToPushNotifications({ successful in
    guard successful else { return }
    // Ensured that subscription was created successfully

// In your AppDelegate

func application(application: UIApplication, didReceiveRemoteNotification userInfo: [NSObject : AnyObject]) {


All CloudKit Attributes are mapped automatically to your CoreData attributes with the exception of CKAsset and CLLocation.

CKAsset and CLLocation can be used by setting the corresponding attribute as Transformable in your CoreData Model.

CloudKit CoreData
NSDate NSDate
NSData NSData
NSString NSString
NSNumber NSNumber
CKReference NSManagedObject
CKAsset Transformable
CLLocation Transformable

Transformable Attributes

CKAsset and CLLocation can be used in your CoreData model as Transformable attributes.

  1. To use CKAsset set Transformable as AttributeType and CKAssetTransformer as value transformer name for the attribute.

  1. To use CLLocation set Transformable as AttributeType and CLLocationTransformer as value transformer name for the attribute.


CoreData Relationship Translation on CloudKit
To - one To one relationships are translated as CKReferences on the CloudKit Servers.
To - many To many relationships are not explicitly created. Seam only creates and manages to-one relationships on the CloudKit Servers.
Example -> If an Employee has a to-one relationship to Department and Department has a to-many relationship to Employee than Seam will only create the former on the CloudKit Servers. It will fullfil the later by using the to-one relationship. If all employees of a department are accessed Seam will fulfil it by fetching all the employees that belong to that particular department.

Note : You must create inverse relationships in your app's CoreData Model or Seam wouldn't be able to translate CoreData Models in to CloudKit Records. Unexpected errors and curroption of data can possibly occur.

Getting Started

Download the demo project. Run it and see the magic as it happens.


tvOS Support ?

tvOS provides no persistent local storage. Seam uses SQLITE file to keep a local copy of your database which is not possible with tvOS.


A list of Apps which are using Seam.


Seam is owned and maintained by Nofel Mahmood.

You can follow him on Twitter and Medium


Seam is available under the MIT license. See the LICENSE file for more info.

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