Swift核心数据批量更新创建重复记录而不是覆盖

Question

看起来好像我的NSPredicate在更新Core Data记录时不起作用。在执行提取请求时，同样的NSPredicate可以正常工作。

当我做了Batch Update，它只是创造了新的重复记录而不是覆盖现有的预期效果。为什么哦为什么？

这里是我的代码，做了更新：​​

let appDelegate = UIApplication.sharedApplication().delegate as AppDelegate 

lazy var managedObjectContext : NSManagedObjectContext? = { 
    if let managedObjectContext = self.appDelegate.managedObjectContext { 
     return managedObjectContext 
    } 
    else { 
     return nil 
    } 
    }() 

func doesMessageExist(id: String) -> Bool { 
    let fetchRequest = NSFetchRequest(entityName: "ChatMessage") 
    let predicate = NSPredicate(format: "id == %@", id) 
    fetchRequest.predicate = predicate 
    fetchRequest.fetchLimit = 1 

    let count = managedObjectContext!.countForFetchRequest(fetchRequest, error: nil) 
    return (count > 0) ? true : false 
} 

func updateMessage(chatMessage: ChatMessage) { 
    var batchRequest = NSBatchUpdateRequest(entityName: "ChatMessage") 

    if doesMessageExist(chatMessage.id) { 
     batchRequest.predicate = NSPredicate(format: "id == %@", chatMessage.id) 
    } 

    batchRequest.propertiesToUpdate = [ 
     "id" : chatMessage.id, 
     "senderUserId" : chatMessage.senderUserId, 
     "senderUsername" : chatMessage.senderUsername, 
     "receiverUserId" : chatMessage.receiverUserId, 
     "receiverUsername" : chatMessage.receiverUsername, 
     "messageType" : chatMessage.messageType, 
     "message" : chatMessage.message, 
     "timestamp" : chatMessage.timestamp 
    ] 

    batchRequest.resultType = .UpdatedObjectsCountResultType 
    var error : NSError? 
    var results = self.managedObjectContext!.executeRequest(batchRequest, error: &error) as NSBatchUpdateResult 
    if error == nil { 
     println("Update Message: \(chatMessage.id) \(results.result)") 
     appDelegate.saveContext() 
    } 
    else { 
     println("Update Message Error: \(error?.localizedDescription)") 
    } 
} 

这里是我的ChatMessage类：

class ChatMessage: NSManagedObject { 

    @NSManaged var id: String 
    @NSManaged var message: String 
    @NSManaged var messageType: String 
    @NSManaged var receiverUserId: String 
    @NSManaged var receiverUsername: String 
    @NSManaged var senderUserId: String 
    @NSManaged var senderUsername: String 
    @NSManaged var timestamp: NSDate 

} 

这里是核心数据堆栈在我的AppDelegate：

lazy var applicationDocumentsDirectory: NSURL = { 
    // The directory the application uses to store the Core Data store file. This code uses a directory named "com.walintukai.LFDate" in the application's documents Application Support directory. 
    let urls = NSFileManager.defaultManager().URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask) 
    return urls[urls.count-1] as NSURL 
}() 

lazy var managedObjectModel: NSManagedObjectModel = { 
    // The managed object model for the application. This property is not optional. It is a fatal error for the application not to be able to find and load its model. 
    let modelURL = NSBundle.mainBundle().URLForResource("LFDate", withExtension: "momd")! 
    return NSManagedObjectModel(contentsOfURL: modelURL)! 
}() 

lazy var persistentStoreCoordinator: NSPersistentStoreCoordinator? = { 
    // The persistent store coordinator for the application. This implementation creates and return a coordinator, having added 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. 
    // Create the coordinator and store 
    var coordinator: NSPersistentStoreCoordinator? = NSPersistentStoreCoordinator(managedObjectModel: self.managedObjectModel) 
    let url = self.applicationDocumentsDirectory.URLByAppendingPathComponent("LFDate.sqlite") 
    var error: NSError? = nil 
    var failureReason = "There was an error creating or loading the application's saved data." 
    if coordinator!.addPersistentStoreWithType(NSSQLiteStoreType, configuration: nil, URL: url, options: nil, error: &error) == nil { 
     coordinator = nil 
     // Report any error we got. 
     let dict = NSMutableDictionary() 
     dict[NSLocalizedDescriptionKey] = "Failed to initialize the application's saved data" 
     dict[NSLocalizedFailureReasonErrorKey] = failureReason 
     dict[NSUnderlyingErrorKey] = error 
     error = NSError(domain: "YOUR_ERROR_DOMAIN", code: 9999, userInfo: dict) 
     // Replace this with code to handle the error appropriately. 
     // abort() 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. 
     NSLog("Unresolved error \(error), \(error!.userInfo)") 
     abort() 
    } 

    return coordinator 
}() 

lazy var managedObjectContext: NSManagedObjectContext? = { 
    // Returns the managed object context for the application (which is already bound to the persistent store coordinator for the application.) This property is optional since there are legitimate error conditions that could cause the creation of the context to fail. 
    let coordinator = self.persistentStoreCoordinator 
    if coordinator == nil { 
     return nil 
    } 
    var managedObjectContext = NSManagedObjectContext() 
    managedObjectContext.persistentStoreCoordinator = coordinator 
    managedObjectContext.mergePolicy = NSOverwriteMergePolicy 
    return managedObjectContext 
}() 

// MARK: - Core Data Saving support 

func saveContext() { 
    dispatch_async(dispatch_get_main_queue(),{ 
     if let moc = self.managedObjectContext { 
      var error: NSError? = nil 
      if moc.hasChanges && !moc.save(&error) { 
       // Replace this implementation with code to handle the error appropriately. 
       // abort() 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. 
       NSLog("Database Save Error: \(error), \(error!.userInfo)") 
       abort() 
      } 
     } 
    }); 
} 

Answer 1

您的doesMessageExist功能是wron G。

您检查计数的读取请求不等于NSNotFound，它只会在错误的情况下做的。如果找不到消息，它将返回零，如果可以找到它，它将返回一个（或更多，如果你有多个具有相同ID的对象）。

目前你的代码会说这个消息总是存在。

顺便提一下，这个问题中的代码都没有创建新的对象，并且executeRequest不是NSManagedObjectContext上的方法，因此您应该在问题中包含您的实现。

Answer 2

可悲的是，对于NSBatchUpdateRequest没有文档（可耻的是你，苹果公司！）。但是，WWDC 2014会话225（这里是ASCII transcript）涵盖了批量更新请求。

在会议上，要提到的是批量更新绕过NSManagedObjectContext和持久存储直接进行更改。所以，你必须自己刷新的对象：

So if you're interested in updating your database en masse, setting a flag on a particular column for example, and then reflecting those changes in the UI, you're going to need to get the results or the Managed Object IDs back, so you can tell the object, tell the Managed Object Context to refresh the objects with those IDs.

您必须指定其他resultType批量要求：

batchRequest.resultType = .UpdatedObjectIDsResultType 

，然后执行请求后，你必须使用的NSManagedObjectID返回数组刷新对象（从Big Nerd Ranch代码示例中，在夫特重写）：

for objectsID in objectsIDs { 
    var error : NSError? = nil 
    if let object = context.existingObjectWithID(objectsID as NSManagedObjectID, error: &error) { 
     context.refreshObject(object, mergeChanges: true) 
    } 
} 

Answer 3

尝试此代码为NSBatchUpdateRequest与出duplicatin g swift中的记录

func batchUpdate{ 
     let appDelegate = UIApplication.shared.delegate as! AppDelegate 
     let managedContext = appDelegate.managedObjectContext 
     let batchRequest = NSBatchUpdateRequest(entityName: "ENTITY_NAME") 
     batchRequest.propertiesToUpdate = [ "PROPERTY_NAME" : "CHANGE_VALUE`enter code here`"] 
     batchRequest.resultType = .updatedObjectIDsResultType 

     do{ 
      let objectIDs = try managedContext.execute(batchRequest) as! NSBatchUpdateResult 
      let objects = objectIDs.result as! [NSManagedObjectID] 

      objects.forEach({ objID in 
       let managedObject = managedContext.object(with: objID) 
       managedContext.refresh(managedObject, mergeChanges: false) 
      }) 
     } catch { 
     } 
}