问题通过Light Migration将CoreData模块版本迁移到更新版本

Question

在我的AppDelegate中，我的persistentStoreCoordinator在选项中启用了NSMigratePersistentStoresAutomaticallyOption和NSInferMappingModelAutomaticallyOption：

    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("knoData.sqlite")

        var error: NSError? = nil

        var failureReason = "There was an error creating or loading the application's saved data."
        let mOptions: NSDictionary = [NSMigratePersistentStoresAutomaticallyOption: true,
            NSInferMappingModelAutomaticallyOption: true]
        if coordinator!.addPersistentStoreWithType(NSSQLiteStoreType, configuration: nil, URL: url, options: mOptions, 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)")

            self.managedObjectContext?.reset()

            abort()

        }

当我升级我的核心数据版本时，它似乎工作没有崩溃，直到我用这段代码获取核心数据：

func fetchCoreData(){
        var error : NSError?
        let appDel : AppDelegate = UIApplication.sharedApplication().delegate as AppDelegate
        let context : NSManagedObjectContext = appDel.managedObjectContext!
        let fetchRequest = NSFetchRequest(entityName:"SavedData")
        let fetchedResults = context.executeFetchRequest(fetchRequest, error: &error) as [data]?
        if let resultsArray = fetchedResults {
            if resultsArray.count > 0 {
                var mostRecentData = resultsArray.count - 1
                let newItem = resultsArray[mostRecentData] as data
                NSLog("NEW ITEM \(newItem)")
                clientID = newItem.userid
                NSLog(clientID)
                knoColor = Int(newItem.knoColor)
                var upKNOs = newItem.upKNOs
                var downKNOs = newItem.downKNOs
                var upKNOString = upKNOs.stringByReplacingOccurrencesOfString("[", withString: "", options: NSStringCompareOptions.LiteralSearch, range: nil)
                upKNOString = upKNOString.stringByReplacingOccurrencesOfString("]", withString: "", options: NSStringCompareOptions.LiteralSearch, range: nil)
                upKNOString = upKNOString.stringByReplacingOccurrencesOfString("\"", withString: "", options: NSStringCompareOptions.LiteralSearch, range: nil)
                upKNOString = upKNOString.stringByReplacingOccurrencesOfString(" ", withString: "", options: NSStringCompareOptions.LiteralSearch, range: nil)
                upKNOArray = upKNOString.componentsSeparatedByString(",")
                var downKNOString = downKNOs.stringByReplacingOccurrencesOfString("[", withString: "", options: NSStringCompareOptions.LiteralSearch, range: nil)
                downKNOString = downKNOString.stringByReplacingOccurrencesOfString("]", withString: "", options: NSStringCompareOptions.LiteralSearch, range: nil)
                downKNOString = downKNOString.stringByReplacingOccurrencesOfString("\"", withString: "", options: NSStringCompareOptions.LiteralSearch, range: nil)
                downKNOString = downKNOString.stringByReplacingOccurrencesOfString(" ", withString: "", options: NSStringCompareOptions.LiteralSearch, range: nil)
                downKNOArray = downKNOString.componentsSeparatedByString(",")
                var index = find(upKNOArray, "")
                if(index != nil){
                    upKNOArray.removeAtIndex(index!)
                }
                var index2 = find(downKNOArray, "")
                if(index2 != nil){
                    downKNOArray.removeAtIndex(index2!)
                }
                censor = newItem.censor
                unit = newItem.distUnit
                radius = newItem.radius
                slideAnimation = newItem.slideAnimation
                handle = newItem.handle
                NSLog("Censor(\(censor)) was set to newItem.censor(\(newItem.censor))")
            } else {
                NSLog("No results from fetch request.")
                var request = HTTPTask()
                request.GET(API, parameters: nil, success: {(response: HTTPResponse) in
                    if response.responseObject != nil {
                        let data = response.responseObject as NSData
                        let str = NSString(data: data, encoding: NSUTF8StringEncoding)
                        self.setFirstCoreData(str!)
                    }
                    },failure: {(error: NSError, response: HTTPResponse?) in
                        NSLog("error: \(error)")
                })
            }
        }
    }

    func setFirstCoreData(id: String){

        //NSLog(device)
        //NSLog("\(screenWidth)")

        let appDel : AppDelegate = UIApplication.sharedApplication().delegate as AppDelegate

        let context : NSManagedObjectContext = appDel.managedObjectContext!

        let entity = NSEntityDescription.entityForName( "SavedData", inManagedObjectContext: context )

        var newItem = data( entity: entity!, insertIntoManagedObjectContext: context )

        var error : NSError?

        newItem.userid = id
        clientID = id
        newItem.upKNOs = "[]"
        newItem.downKNOs = "[]"
        knoColor = Int(arc4random_uniform(UInt32(colors.count)))
        newItem.knoColor = Int32(knoColor!)
        newItem.censor = false
        newItem.distUnit = Int32(0)
        newItem.radius = Double(2.5)
        newItem.slideAnimation = true
        newItem.handle = handle
        unit = newItem.distUnit
        radius = newItem.radius
        slideAnimation = newItem.slideAnimation
        if !context.save(&error) {
            NSLog("Unresolved error \(error), \(error!.userInfo)")
        }

        NSLog("CoreData(newItem):\(newItem)")
        NSLog("CoreData(newItem.description):\(newItem.description)")
    }

代码没有问题，因为它在我更新核心数据模型之前一直有效，我最终在这里得到了一个EXC_BAD_ACCESS错误：

我认为我的问题是我尝试访问的属性没有初始值，但我不确定解决方案，因为我之前从未使用过Core Data Migrations。