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Cloudkit based persistent store for Core Data
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paulw11/Seam3
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Seam3 is a framework built to bridge gaps between CoreData and CloudKit. It almost handles all the CloudKit hassle.All you have to do is use it as a store type for your CoreData store.Local caching and sync is taken care of.
Seam3 is based onSeam bynofelmahmood
Changes in Seam3 include:
- Corrects one-to-many and many-to-one relationship mapping between CoreData and CloudKit
- Adds mapping between binary attributes in CoreData and CKAssets in CloudKit
- Code updates for Swift 3.0 on iOS 10, Mac OS 10.11 & tvOS 10
- Restructures code to eliminate the use of global variables
| CoreData | CloudKit |
|---|---|
| NSDate | Date/Time |
| Binary Data | Bytes or CKAsset (See below) |
| NSString | String |
| Integer16 | Int(64) |
| Integer32 | Int(64) |
| Integer64 | Int(64) |
| Decimal | Double |
| Float | Double |
| Boolean | Int(64) |
| NSManagedObject | Reference |
In the table above :Integer16,Integer32,Integer64,Decimal,Float andBoolean are referring to the instance ofNSNumber usedto represent them in CoreData Models.NSManagedObject refers to ato-one relationship in a CoreData Model.
If aBinary Data attribute has theAllows External Storage option selected, it will be stored as aCKAsset in Cloud Kit, otherwise it will be stored asBytes in theCKRecord itself.
| 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. Seam3 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 Seam3 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 Seam3 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 Seam3 wouldn't be able to translate CoreData Models in to CloudKit Records. Unexpected errors and corruption of data can possibly occur.
Seam3 keeps the CoreData store in sync with the CloudKit Servers. It let's you know when the sync operation starts and finishes by throwing the following two notifications.
smSyncDidStartNotificationsmSyncDidFinishNotification
If an error occurred during the sync operation, then theuserInfo property of thesmSyncDidFinish notification will contain anError object for the keySMStore.SMStoreErrorDomain
In case of any sync conflicts, Seam3 exposes 3 conflict resolution policies.
clientTellsWhichWins
This policy requires you to set thesyncConflictResolutionBlock property of yourSMStore. The closure you specify will receive threeCKRecord arguments; The first is the current server record. The second is the current client record and the third is the client record before the most recent change. Your closure must modify and return the server record that was passed as the first argument.
serverRecordWins
This is the default. It considers the server record as the true record.
clientRecordWins
This considers the client record as the true record.
- Declare a SMStore type property in the class where your CoreData stack resides.
varsmStore:SMStore?
- For iOS9 and earlier or macOS, add a store type of
SMStore.typeto your app's NSPersistentStoreCoordinator and assign it to the property created in the previous step.
SMStore.registerStoreClass()do{self.smStore=try coordinator.addPersistentStoreWithType(SMStore.type, configuration:nil, URL: url, options:nil)as?SMStore}
- For iOS10 using
NSPersistentContainer:
lazyvarpersistentContainer:NSPersistentContainer={SMStore.registerStoreClass()letcontainer=NSPersistentContainer(name:"Seam3Demo2")leturls=FileManager.default.urls(for:.documentDirectory, in:.userDomainMask)iflet applicationDocumentsDirectory= urls.last{leturl= applicationDocumentsDirectory.appendingPathComponent("SingleViewCoreData.sqlite")letstoreDescription=NSPersistentStoreDescription(url: url) storeDescription.type=SMStore.type container.persistentStoreDescriptions=[storeDescription] container.loadPersistentStores(completionHandler:{(storeDescription, error)iniflet error= errorasNSError?{ // 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}fatalError("Unable to access documents directory")}()
By default, logs will be written toos_log, but you can route log messages to your own class by extendingSMLogger:
classAppDelegate:SMLogDelegate{func application(_ application:UIApplication, didFinishLaunchingWithOptions launchOptions:[UIApplication.LaunchOptionsKey:Any]?)->Bool{SMStore.logger=self} // MARK: SMLogDelegatefunc log(_ message:@autoclosure()->String, type:SMLogType){#if DEBUGswitch type{case.debug:print("Debug:\(message())")case.info:print("Info:\(message())")case.error:print("Error:\(message())")case.fault:print("Fault:\(message())")case.defaultType:print("Default:\(message())")}#endif}}
You can access theSMStore instance using:
self.smStore = container.persistentStoreCoordinator.persistentStores.first as? SMStoreBefore triggering a sync, you should check the Cloud Kit authentication status and check for a changed Cloud Kit user:
self.smStore?.verifyCloudKitConnectionAndUser() { (status, user, error) in guard status == .available, error == nil else { NSLog("Unable to verify CloudKit Connection \(error)") return } guard let currentUser = user else { NSLog("No current CloudKit user") return } var completeSync = false let previousUser = UserDefaults.standard.string(forKey: "CloudKitUser") if previousUser != currentUser { do { print("New user") try self.smStore?.resetBackingStore() completeSync = true } catch { NSLog("Error resetting backing store - \(error.localizedDescription)") return } } UserDefaults.standard.set(currentUser, forKey:"CloudKitUser") self.smStore?.triggerSync(complete: completeSync)}- Enable Push Notifications for your app.
- Implement didReceiveRemoteNotification Method in your AppDelegate and call
handlePushon the instance of SMStore created earlier.
func application(_ application:UIApplication, didReceiveRemoteNotification userInfo:[AnyHashable:Any], fetchCompletionHandler completionHandler:@escaping(UIBackgroundFetchResult)->Void){print("Received push") smStore?.handlePush(userInfo: userInfo){(result)incompletionHandler(result.uiBackgroundFetchResult)}}
- Enjoy
The default Cloud Kit container is named using your app or application'sbundle identifier. If you want to share Cloud Kit data between apps on different platforms (e.g. iOS and macOS) then you need to use a named Cloud Kit container. You can specify a cloud kit container when you create your SMStore instance.
On iOS10, specify theSMStore.SMStoreContainerOption using theNSPersistentStoreDescription object
let storeDescription = NSPersistentStoreDescription(url: url)storeDescription.type = SMStore.typestoreDescription.setOption("iCloud.org.cocoapods.demo.Seam3-Example" as NSString, forKey: SMStore.SMStoreContainerOption)On iOS9 and macOS specify an options dictionary to the persistent store coordinator
let options:[String:Any] = [SMStore.SMStoreContainerOption:"iCloud.org.cocoapods.demo.Seam3-Example"]self.smStore = try coordinator!.addPersistentStore(ofType: SMStore.type, configurationName: nil, at: url, options: options) as? SMStoreEnsure that you specify the value you specify is selected underiCloud containers on thecapabilities tab for your app in Xcode.
Migration should be quite straight-forward, as the format used to store data in CloudKit and in the local backing store haven't changed.Change the import statement toimport Seam3 and you should be good to go.
To run the example project, clone the repo, and runpod install from the Example directory first. If you are running on the simulator, make sure that you log in to iCloud using the settings app in the simulator.
Seam3 is available throughCocoaPods. To installit, simply add the following line to your Podfile:
pod"Seam3"
paulw,paulw@wilko.me
Seam3 is available under the MIT license. See the LICENSE file for more info.
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Cloudkit based persistent store for Core Data