核心数据上下文不保存

Posted 2023-03-12

【中文标题】核心数据上下文不保存

【英文标题】：Core Data Context not Saving

【发布时间】：2015-03-24 16:31:16

【问题描述】：

我一直在努力让 Core Data 在我的移动应用程序中运行。在我尝试修复它之后，这些值始终保持为零。这是保存我的信息的相关信息，请注意，任何时候都只会有一个结果。

var appDel:AppDelegate = (UIApplication.sharedApplication().delegate as AppDelegate)
var context:NSManagedObjectContext = appDel.managedObjectContext!
let insertBools = NSEntityDescription.insertNewObjectForEntityForName("Codes", inManagedObjectContext: context) as NSManagedObject

稍后在根据扫描的二维码进行字符串检查比较后的代码中......

else if (metadataObj.stringValue == "oiu2162poiu" && res.qrCode5_Found != true) 
    captureSession?.stopRunning()
    println("\(metadataObj.stringValue) qrCode5_Found if")
    insertBools.setValue(true, forKey: "qrCode5_Found")
    var alert = UIAlertController(title: "Code Found!", message: "You have found and scanned Code #5!", preferredStyle: UIAlertControllerStyle.Alert)
    alert.addAction(UIAlertAction(title: "OK", style: UIAlertActionStyle.Default, handler: nil))
    self.presentViewController(alert, animated: true, completion: nil)
    insertBools.managedObjectContext?.save(nil)
    self.navigationController?.popViewControllerAnimated(false)

我不确定我哪里出错了。在此之前的 View 控制器每次加载时都会检索每个键的值，并根据是否找到某些元素显示某些标签（这是应用程序的寻宝风格部分）。

override func viewDidLoad() 
    super.viewDidLoad()
    var appDel:AppDelegate = (UIApplication.sharedApplication().delegate as AppDelegate)
    var context:NSManagedObjectContext = appDel.managedObjectContext!
    let request = NSFetchRequest(entityName: "Codes")
    request.returnsObjectsAsFaults = false

    var results:NSArray = context.executeFetchRequest(request, error: nil)!

    if (results.count == 1) 
        var res = results[0] as Codes
        if (res.qrCode1_Found != true) 
            qrCode1.enabled = true
            scanQRCodeButton.enabled = true
            qrLeftList.enabled = true
        
        if (res.qrCode2_Found != true) 
            qrCode2.enabled = true
            scanQRCodeButton.enabled = true
            qrLeftList.enabled = true
        
        if (res.qrCode3_Found != true) 
            qrCode3.enabled = true
            scanQRCodeButton.enabled = true
            qrLeftList.enabled = true
        
        if (res.qrCode4_Found != true) 
            qrCode4.enabled = true
            scanQRCodeButton.enabled = true
            qrLeftList.enabled = true
        
        if (res.qrCode5_Found != true) 
            qrCode5.enabled = false
            scanQRCodeButton.enabled = true
            qrLeftList.enabled = true
        
        if (res.qrCode5_Found == true && res.qrCode4_Found == true && res.qrCode3_Found == true && res.qrCode2_Found == true && res.qrCode1_Found == true) 
            registerButton.enabled = true
            scanQRCodeButton.enabled = false
        
    
........

还有我的 AppDelegate 文件，我最初没有包含 Core Data，但我手动导入了它，编译器没有抛出任何错误。

//
//  AppDelegate.swift
//  webview_test
//
//  Created by Robert on 3/19/15.
//  Copyright (c) 2015 Robert. All rights reserved.
//

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.

// 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 "com.xxxx.ProjectName" 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("SavedVariables", 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("webview_test.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.
        var dict = [String: AnyObject]()
        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
    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()
        
    


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()

作为旁注...如果有人能告诉我如何强制程序等待用户按下警报上的“确定”按钮，然后再继续，我将永远欠你的债。

【参考方案1】：

我误解了 Core Data 的概念。相反，我现在循环遍历每个结果而不是

var res = results[0] as Codes

与

for res in results as [NSManagedObject] 
    ....

得到我需要的结果，然后使用这些结果进行比较，这是一种粗制滥造的工作，但它确实有效。

【讨论】：

我有同样的问题。我有以下代码： var conf = NSEntityDescription.insertNewObjectForEntityForName("Configuration", inManagedObjectContext: managedObjectContext!) as Configuration conf.terms_accepted = "1" 每次它创建一个新对象。每次添加一个新对象时： println(managedObjectContext!.executeFetchRequest(fReq, error:&error)?.count) 我不知道这是错误还是正确