使用Swift将CoreData实现到现有项目中 [英] Implement CoreData into an existing project using Swift
问题描述
我目前使用Xcode 6 beta 7，并决定我需要CoreData已经创建我的项目。我已经看过一些问题已经要求这个目标C与观看视频的主题，但我似乎得到了同样的错误。至于我对CoreData框架本身的使用，我很确定它是正确的，因为我创建了另一个空项目（与CoreData框检查），并遵循相同的实现，它的工作方式像一个魅力，但可能有一些问题，我也在那里。所以这里是我在Swift中的项目中实现CoreData的步骤。
I am currently using Xcode 6 beta 7 and decided I needed CoreData after already creating my project. I have looked at some of the questions already asking this for objective C along with watching videos on the subject but I seem to be getting the same error. As for my usage of the CoreData framework itself, I am pretty sure it is correct as I created another empty project (with the CoreData box checked) and followed the same implementation and it worked like a charm but there may be something wrong I'm doing there too. So here are the steps I followed to implement CoreData in my project in Swift. Any help is appreciated.
步骤1：在Build Phases下通过Link Binary with Libraries选项卡添加CoreData框架
Step 1: I added the CoreData framework through "Link Binary with Libraries" tab under "Build Phases"
步骤2：然后我去了我的任何.swift文件，需要实现CoreData（appDelegate.swift和另一个文件，现在），并添加行：
Step 2: I then went to any of my .swift files which would need to implement CoreData (appDelegate.swift and one other file as of now) and added the line:
import CoreData
。
步骤3：我使用名为cData的实体创建了一个数据列表，然后创建了一个名为data.swift的类。这里是data.swift：
Step 3: I created a data list with an entity called "cData", then made a class for it called "data.swift". Here is data.swift:
import UIKit
import CoreData
@objc( data )
class data: NSManagedObject {
@NSManaged var something : String
}
$ b b
步骤4：我写的代码实际保存数据在另一个文件：
Step 4: I wrote the code to actually save the data in another file:
@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)
}
$ b b
步骤5：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（所以我可以命名为同一件事），并检查CoreData框。然后我将整个appDelegate.swift从这个项目复制到我当前的项目。这是我的appDelegate.swift：
Step 5: Here is where I believe I messed up, though I could be wrong. I created a new project on a separate Mac (so I could name it the same thing) and checked the CoreData box. I then copied the entire appDelegate.swift from this project to my current one. Here is my 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 inactive 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()
}
}
}
}
一旦调用IBAction方法useCoreData，我就会崩溃，致命错误：在解包可选值
（lldb）时意外找到nil，并指出违规行在appDelegate.swift中：
Once the IBAction method "useCoreData" is called, I get a crash and the exception states "fatal error: unexpectedly found nil while unwrapping an Optional value (lldb)" and states the offending line is in appDelegate.swift:
let modelURL = NSBundle.mainBundle().URLForResource("my_app", withExtension: "momd")!
同样，当我在另一个项目中尝试这个相同的CoreData实现时， - 它，它的工作原理像一个魅力。我看到一个类似的问题，这样（用户得到相同的错误），但似乎不是他的问题也解决了。
Again, when I try this same CoreData implementation in another project that had the CoreData box checked from the get-go, it works like a charm. I saw a similar question like this (the user was getting the same error), but it doesn't seem like his problem was solved either. Again any help is appreciated and thanks in advance!
推荐答案
你得到一个 nil
You're getting an nil value there because the file it's looking for doesn't exist in your main bundle.
您需要从您创建的其他项目中复制数据模型文件到您的主要项目。该文件将被称为 My_App.xcdatamodeld ，并应位于您的Xcode项目文件所在的文件夹中。
You need to copy your data model file from the other project you created to your main project. The file would be called something like My_App.xcdatamodeld and should be located in the same folder that your Xcode project file is in.
注意： URLForResource 行正在寻找 My_App.momd ;该文件由Xcode从 My_App.xcdatamodeld 在编译项目时创建。
Note: The URLForResource line is looking for My_App.momd; that file is created by Xcode from My_App.xcdatamodeld when it compiles your project.
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