Ios Swift核心数据批量更新创建重复记录而不是覆盖

更新

核心数据

记录时，我的

NSPredicate

似乎不起作用。执行提取请求时，相同的

NSPredicate

不会出现问题

当我执行批更新时，它只会创建新的重复记录，而不是按预期覆盖现有记录。为什么，为什么

以下是我进行更新的代码：

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)")
    }
}

这是我的聊天信息课程：

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

}

以下是我的AppDelegate中的核心数据堆栈：

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()
            }
        }
    });
}

---

您的

doesMessageExist

函数错误

您可以检查取回请求的计数是否不等于

NSNotFound

，只有在出现错误时才会这样做。如果找不到消息，它将返回零，如果可以找到，它将返回一个（或多个，如果您有多个具有相同ID的对象）

此时，您的代码将表明消息始终存在

---

顺便说一句，本问题中的任何代码都没有创建新对象，而且

executeRequest

不是NSManagedObjectContext上的方法，因此您可能应该在问题中包含该方法的实现

遗憾的是，没有关于

NSBatchUpdateRequest

的文档（你真丢脸，苹果！）。但批量更新请求已在WWDC 2014第225次会议上讨论过（以下是示例）

在会话中，提到批量更新绕过

NSManagedObjectContext

，直接在持久存储中进行更改。因此，您必须自己刷新对象：

因此，如果您想整体更新数据库，例如在特定列上设置一个标志，然后在UI中反映这些更改，则需要返回结果或托管对象ID，这样您就可以告诉对象，告诉托管对象上下文使用这些ID刷新对象

您必须为批处理请求指定其他

resultType

：

batchRequest.resultType = .UpdatedObjectIDsResultType

然后在执行请求后，您必须使用返回的

NSManagedObjectID

数组刷新对象（代码示例来自，用Swift重写）：

---

在不复制swift3中的记录的情况下，尝试NSBatchUpdateRequest的此代码

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 {
        }
}

---

谢谢你的回复。我将我的

doesMessageExist

return函数更改为：

return（count>0）？真：假。另外，
executeRequest
函数是我的
NSManagedObjectContext
的默认函数。我没有实现
扩展
。我只是按照这个方向做的。我知道它正在制作重复的记录，因为这个println消息：
println（“更新消息：\（chatMessage.id）\（results.result）”）
。每当执行更新时，results.result编号都会不断增加。
executeRequest（）
和
NSBatchUpdateRequest
在iOS 8.0中引入。它列在中，但尚未涵盖它。@MartinR
executeRequest
可能尚未包含在类引用中，但它肯定正在工作，并且确实对我的
核心数据进行了更改。尽管如此，如果它工作正常是另一回事，因为它没有注意我的
NSPredicate
@TheNomad：我的评论只是对jrturton的声明“executeRequest不是NSManagedObjectContext上的方法”的回应。@martinr我认为它是持久存储协调器上的方法，而不是上下文？我希望他们能让文档保持最新。这是一个巨大的进步，而文档中没有它？拜托，苹果我不明白你为什么想让它执行I/O。相反，你可能应该使用
objectRegisteredForID
？现在是2021年，苹果还没有对此进行记录。不 真实 的！马斯潘雷恩格-尼恩格，塞里卡-维达雷恩格，马拉纳马斯马斯。
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 {
        }
}