使用Swift将CoreData实现到现有项目中

Question

我正在使用Xcode 6 beta 7，并且决定在创建项目后需要CoreData。我已经看过一些已经问过这个问题的问题，以及观看关于这个主题的视频，但是我似乎也得到了同样的错误。至于我自己使用CoreData框架，我非常肯定它是正确的，因为我创建了另一个空项目（CoreData框被选中），并遵循相同的实现，它的工作方式像一个魅力，但可能会出现问题，我是也在那里做。所以下面是我在Swift项目中实现CoreData的步骤。

第1步：我通过“链接二进制与库”选项卡中添加了CoreData框架

步骤2在“构建阶段”：然后我去了我的任何.swift文件，这需要实现CoreData（的appDelegate .swift和另一个文件截至目前）并添加了行：

import CoreData 

顶部。

第3步：我创建了一个名为“cData”的实体的数据列表，然后为它创建了一个名为“data.swift”的类。这里是data.swift：

import UIKit 
import CoreData 

@objc(data) 
class data: NSManagedObject { 
    @NSManaged var something : String 
} 

第4步：我写的代码实际上将数据保存在另一个文件：

@IBAction func useCoreData(sender: AnyObject) 
    { 
     let AD : AppDelegate = UIApplication.sharedApplication().delegate as AppDelegate 
     let ct : NSManagedObjectContext = AD.managedObjectContext! 
     let ent = NSEntityDescription.entityForName("CData", inManagedObjectContext: ct) 
     var dat = data(entity: ent!, insertIntoManagedObjectContext: ct) 
     dat.something = someTextField.text 
     ct.save(nil) 

     println(dat) 
    } 

第5步：这里是我相信我搞砸了，虽然我可能是错的。我在一个单独的Mac上创建了一个新项目（所以我可以将它命名为相同的东西）并检查CoreData框。然后，我将这个项目中的整个appDelegate.swift复制到当前的项目中。这里是我的appDelegate.swift：

import UIKit 
import CoreData 

@UIApplicationMain 

class AppDelegate: UIResponder, UIApplicationDelegate { 
    var window: UIWindow? 

    func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool { 
     // Override point for customization after application launch. 
     return true 
    } 

    func applicationWillResignActive(application: UIApplication) { 
     // Sent when the application is about to move from active to inactive state. This can occur for certain types of temporary interruptions (such as an incoming phone call or SMS message) or when the user quits the application and it begins the transition to the background state. 
     // Use this method to pause ongoing tasks, disable timers, and throttle down OpenGL ES frame rates. Games should use this method to pause the game. 
    } 

    func applicationDidEnterBackground(application: UIApplication) { 
     // Use this method to release shared resources, save user data, invalidate timers, and store enough application state information to restore your application to its current state in case it is terminated later. 
     // If your application supports background execution, this method is called instead of applicationWillTerminate: when the user quits. 
    } 

    func applicationWillEnterForeground(application: UIApplication) { 
     // Called as part of the transition from the background to the active state; here you can undo many of the changes made on entering the background. 
    } 

    func applicationDidBecomeActive(application: UIApplication) { 
     // Restart any tasks that were paused (or not yet started) while the application was inactive. If the application was previously in the background, optionally refresh the user interface. 
    } 

    func applicationWillTerminate(application: UIApplication) { 
     // Called when the application is about to terminate. Save data if appropriate. See also applicationDidEnterBackground:. 
     // Saves changes in the application's managed object context before the application terminates. 
     self.saveContext() 
    } 

    // MARK: - Core Data stack 

    lazy var applicationDocumentsDirectory: NSURL = { 
     // The directory the application uses to store the Core Data store file. This code uses a directory named "y.Simple_Grade" 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("my_app", 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("my_app.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.errorWithDomain("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 
     return managedObjectContext 
     }() 

    // MARK: - Core Data Saving support 

    func saveContext() { 
     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("Unresolved error \(error), \(error!.userInfo)") 
       abort() 
      } 
     } 
    } 
} 

一旦IBAction为方法“useCoreData”之称，我得到一个崩溃和异常状态“致命错误：意外发现零而展开的可选值 （LLDB）”和状态有问题的行是appDelegate.swift：

let modelURL = NSBundle.mainBundle().URLForResource("my_app", withExtension: "momd")! 

同样，当我尝试在其他项目有CoreData盒从一开始走了，它就像一个魅力选中此相同CoreData实施。我看到类似的问题（用户得到同样的错误），但似乎他的问题也没有解决。

Answer 1

因为您要查找的文件在您的主包中不存在，所以您将获得nil值。

您需要将您创建的其他项目的数据模型文件复制到主项目中。该文件将被称为像My_App.xcdatamodeld并应设在你的Xcode项目文件在同一文件夹

注：的URLForResource线正在寻找My_App.momd;该文件在编译项目时由My_App.xcdatamodeld的Xcode创建。