无法创建映射策略 - iOS Core Data

Question

我一直在尝试在我正在整合的应用程序中使用自定义迁移策略。到目前为止，在使用映射模型时，迁移已经从 v1 -> v2 开始。但是，每当我向实体映射添加自定义策略时，迁移都拒绝适用于 v2 -> v3。

自定义迁移策略：

import Foundation
import CoreData

class ObjectCustomV2V3Migration: NSEntityMigrationPolicy {

override func createDestinationInstancesForSourceInstance(sInstance: NSManagedObject, entityMapping mapping: NSEntityMapping, manager: NSMigrationManager, error: NSErrorPointer) -> Bool {

    var newObject:NSManagedObject? = NSEntityDescription.insertNewObjectForEntityForName(mapping.destinationEntityName!, inManagedObjectContext: manager.destinationContext) as? NSManagedObject

    // Sets attr31 - string attribute
    var str:String = sInstance.valueForKey("attr21") as String
    if str == "" {
        str = "BlanketyBlank"
    }
    newObject?.setValue(str, forKey: "attr31")

    // Sets attr32 (int16 attribute) as double of value in previous version
    // ignore the dodgy type casting.
    var num:Int = sInstance.valueForKey("attr22") as Int
    num *= 2
    var num16 = NSNumber(integer: num)

    newObject?.setValue(num16, forKey: "attr32")



    if newObject != nil {
        manager.associateSourceInstance(sInstance, withDestinationInstance: newObject!, forEntityMapping: mapping)
        return true
    }


    return false


   }
}

当我运行应用程序时，返回以下错误：

2015-07-10 14:32:42.952 SingleDBMigration[2153:739674] CoreData: error: -addPersistentStoreWithType:SQLite configuration:(null) URL:file:///var/mobile/Containers/Data/Application/6C142EC2-02DB-4BD6-8428-5739C57C7795/Documents/SingleDBMigration.sqlite options:{
    NSInferMappingModelAutomaticallyOption = 0;
    NSMigratePersistentStoresAutomaticallyOption = 1;
} ... returned error Error Domain=NSCocoaErrorDomain Code=134110 "The operation couldn’t be completed. (Cocoa error 134110.)" UserInfo=0x17ecad70 {NSUnderlyingException=Couldn't create mapping policy for class named (ObjectCustomV2V3Migration)} with userInfo dictionary {
    NSUnderlyingException = "Couldn't create mapping policy for class named (ObjectCustomV2V3Migration)";
}
2015-07-10 14:32:42.965 SingleDBMigration[2153:739674] Unresolved error Optional(Error Domain=YOUR_ERROR_DOMAIN Code=9999 "Failed to initialize the application's saved data" UserInfo=0x17eaf880 {NSLocalizedDescription=Failed to initialize the application's saved data, NSUnderlyingError=0x17ecad90 "The operation couldn’t be completed. (Cocoa error 134110.)", NSLocalizedFailureReason=There was an error creating or loading the application's saved data.}), Optional([NSLocalizedDescription: Failed to initialize the application's saved data, NSUnderlyingError: Error Domain=NSCocoaErrorDomain Code=134110 "The operation couldn’t be completed. (Cocoa error 134110.)" UserInfo=0x17ecad70 {NSUnderlyingException=Couldn't create mapping policy for class named (ObjectCustomV2V3Migration)}, NSLocalizedFailureReason: There was an error creating or loading the application's saved data.])

重要的部分是：

NSUnderlyingException=Couldn't create mapping policy for class named (ObjectCustomV2V3Migration)

我已经尝试了我在这个问题上找到的几个问题，但没有一个提供任何令人满意的解决方案。如果有人能阐明我所面临的问题，我将不胜感激！

谢谢！

Answer 1

在了解了类似问题的答案后，我最终解决了这个问题。我忘记添加项目命名空间，所以与其在映射模型中将自定义策略名称设置为ObjectCustomV2V3Migration，我应该使用ProjectModuleName.ObjectCustomV2V3Migration。

Answer 2

我的问题是我的项目名称中有空格，因此在映射模型编辑器中，在指定 Swift 模块名称时，应使用下划线而不是空格来指定自定义策略。

例如，要在名为 My App Name 的项目中指定 MyCustomMigrationPolicy 类，我在编辑器中使用了以下自定义策略：

My_App_Name.MyCustomMigrationPolicy