将核心数据添加到现有的iPhone项目中

我想将核心数据添加到现有的iPhone项目中，但我仍然遇到很多编译错误：

- NSManagedObjectContext undeclared - Expected specifier-qualifier-list before 'NSManagedObjectModel' - ... 

我已经将核心数据框架添加到目标（右键单击我的项目“Targets”，“Add” – “Existing Frameworks”，“CoreData.framework”）。

我的头文件：

 NSManagedObjectModel *managedObjectModel; NSManagedObjectContext *managedObjectContext; NSPersistentStoreCoordinator *persistentStoreCoordinator; [...] @property (nonatomic, retain, readonly) NSManagedObjectModel *managedObjectModel; @property (nonatomic, retain, readonly) NSManagedObjectContext *managedObjectContext; @property (nonatomic, retain, readonly) NSPersistentStoreCoordinator *persistentStoreCoordinator; 

我错过了什么？ 开始一个新项目不是一个选择……

非常感谢！

编辑对不起，我确实有这些实现…但似乎缺少库…实现方法充满了编译错误，如“ managedObjectContext undeclared NSPersistentStoreCoordinator undeclared ”，“ NSPersistentStoreCoordinator undeclared ”，但也有“预期’）’之前NSManagedObjectContext “（虽然看起来括号是正确的）…

 #pragma mark - #pragma mark Core Data stack /** Returns the managed object context for the application. If the context doesn't already exist, it is created and bound to the persistent store coordinator for the application. */ - (NSManagedObjectContext *) managedObjectContext { if (managedObjectContext != nil) { return managedObjectContext; } NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinator]; if (coordinator != nil) { managedObjectContext = [[NSManagedObjectContext alloc] init]; [managedObjectContext setPersistentStoreCoordinator: coordinator]; } return managedObjectContext; } /** Returns the managed object model for the application. If the model doesn't already exist, it is created by merging all of the models found in application bundle. */ - (NSManagedObjectModel *)managedObjectModel { if (managedObjectModel != nil) { return managedObjectModel; } managedObjectModel = [[NSManagedObjectModel mergedModelFromBundles:nil] retain]; return managedObjectModel; } /** Returns the persistent store coordinator for the application. If the coordinator doesn't already exist, it is created and the application's store added to it. */ - (NSPersistentStoreCoordinator *)persistentStoreCoordinator { if (persistentStoreCoordinator != nil) { return persistentStoreCoordinator; } NSURL *storeUrl = [NSURL fileURLWithPath: [[self applicationDocumentsDirectory] stringByAppendingPathComponent: @"Core_Data.sqlite"]]; NSError *error = nil; persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]]; if (![persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeUrl options:nil error:&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. If it is not possible to recover from the error, display an alert panel that instructs the user to quit the application by pressing the Home button. Typical reasons for an error here include: * The persistent store is not accessible * The schema for the persistent store is incompatible with current managed object model Check the error message to determine what the actual problem was. */ NSLog(@"Unresolved error %@, %@", error, [error userInfo]); abort(); } return persistentStoreCoordinator; } 

Answer 1

所有CoreData头文件都在App_Prefix.pch中导入，因此CoreData类将在整个Project中可用，因此您不必手动导入所需文件中的头。

所以打开Xcode并寻找像App_Prefix.pch这样的文件，默认情况下它在Other Sources组中。 在UIKit import语句之后，添加以下行：

 #import  

你应该准备好了。

Xcode 4

对于在Xcode 4中创建的项目，可以在Project导航器的Supporting Files组中找到前缀文件。 它默认称为’ projectname -Prefix.pch’。

Xcode 6+

从Xcode 6开始，默认情况下不再包含预编译的头文件。 这是因为引入了模块，它们不需要使用预编译的头文件。 虽然仍然可以手动添加PCH文件以全局包含CoreData标头，但请考虑使用@import CoreData;指定CoreData依赖关系@import CoreData; *在每个使用CoreData的文件中。 这使得依赖关系明确，更重要的是将来会避免这个问题的问题。

_{* 需要启用模块才能使其正常工作。}

Answer 2

只是为了阐述您实际需要执行的将Core Data添加到以前没有它的项目的所有步骤：

第1步：添加框架

点击您的应用目标（在左侧窗格中，它的顶部图标带有您应用的名称），然后转到“构建阶段”标签，然后点击“链接二进制文件库”，点击底部的小“+”然后查找’CoreData.framework’并将其添加到您的项目中

然后使用以下方法在所有需要的对象上导入coredata（非性感方式）：

迅速

 import CoreData 

目标C.

 #import  

或者在.pch文件中添加常见导入下面的导入（更加性感），如下所示：

 #ifdef __OBJC__ #import  #import  #import  #endif 

第2步：添加数据模型

要添加.xcdatamodel文件，请右键单击/按住Control键并单击右侧窗格中的文件（如在“资源”文件夹中保存），然后选择“添加新文件”，在选择文件类型时单击“核心数据”选项卡，然后单击“确定”。数据模型’，给它一个名称，然后单击下一步和完成，它将把它添加到您的项目中。 当您单击此Model对象时，您将看到用您想要的任何关系将实体添加到项目的界面。

第3步：更新App Delegate

在AppDelegate.swift上的Swift中

 //replace the previous version of applicationWillTerminate with this 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() } func saveContext () { var error: NSError? = nil let managedObjectContext = self.managedObjectContext if managedObjectContext != nil { if managedObjectContext.hasChanges && !managedObjectContext.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. //println("Unresolved error \(error), \(error.userInfo)") abort() } } } // #pragma mark - Core Data stack // Returns the managed object context for the application. // If the context doesn't already exist, it is created and bound to the persistent store coordinator for the application. var managedObjectContext: NSManagedObjectContext { if !_managedObjectContext { let coordinator = self.persistentStoreCoordinator if coordinator != nil { _managedObjectContext = NSManagedObjectContext() _managedObjectContext!.persistentStoreCoordinator = coordinator } } return _managedObjectContext! } var _managedObjectContext: NSManagedObjectContext? = nil // Returns the managed object model for the application. // If the model doesn't already exist, it is created from the application's model. var managedObjectModel: NSManagedObjectModel { if !_managedObjectModel { let modelURL = NSBundle.mainBundle().URLForResource("iOSSwiftOpenGLCamera", withExtension: "momd") _managedObjectModel = NSManagedObjectModel(contentsOfURL: modelURL) } return _managedObjectModel! } var _managedObjectModel: NSManagedObjectModel? = nil // Returns the persistent store coordinator for the application. // If the coordinator doesn't already exist, it is created and the application's store added to it. var persistentStoreCoordinator: NSPersistentStoreCoordinator { if !_persistentStoreCoordinator { let storeURL = self.applicationDocumentsDirectory.URLByAppendingPathComponent("iOSSwiftOpenGLCamera.sqlite") var error: NSError? = nil _persistentStoreCoordinator = NSPersistentStoreCoordinator(managedObjectModel: self.managedObjectModel) if _persistentStoreCoordinator!.addPersistentStoreWithType(NSSQLiteStoreType, configuration: nil, URL: storeURL, options: nil, error: &error) == nil { /* 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. Typical reasons for an error here include: * The persistent store is not accessible; * The schema for the persistent store is incompatible with current managed object model. Check the error message to determine what the actual problem was. If the persistent store is not accessible, there is typically something wrong with the file path. Often, a file URL is pointing into the application's resources directory instead of a writeable directory. If you encounter schema incompatibility errors during development, you can reduce their frequency by: * Simply deleting the existing store: NSFileManager.defaultManager().removeItemAtURL(storeURL, error: nil) * Performing automatic lightweight migration by passing the following dictionary as the options parameter: [NSMigratePersistentStoresAutomaticallyOption: true, NSInferMappingModelAutomaticallyOption: true} Lightweight migration will only work for a limited set of schema changes; consult "Core Data Model Versioning and Data Migration Programming Guide" for details. */ //println("Unresolved error \(error), \(error.userInfo)") abort() } } return _persistentStoreCoordinator! } var _persistentStoreCoordinator: NSPersistentStoreCoordinator? = nil // #pragma mark - Application's Documents directory // Returns the URL to the application's Documents directory. var applicationDocumentsDirectory: NSURL { let urls = NSFileManager.defaultManager().URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask) return urls[urls.endIndex-1] as NSURL } 

在Objective C中，确保将这些对象添加到AppDelegate.h中

  @property (nonatomic, retain, readonly) NSManagedObjectModel *managedObjectModel; @property (nonatomic, retain, readonly) NSManagedObjectContext *managedObjectContext; @property (nonatomic, retain, readonly) NSPersistentStoreCoordinator *persistentStoreCoordinator; - (NSURL *)applicationDocumentsDirectory; // nice to have to reference files for core data 

合成AppDelegate.m中的前一个对象，如下所示：

 @synthesize managedObjectContext = _managedObjectContext; @synthesize managedObjectModel = _managedObjectModel; @synthesize persistentStoreCoordinator = _persistentStoreCoordinator; 

然后将这些方法添加到AppDelegate.m（确保将您添加的模型的名称放在显示的位置）：

 - (void)saveContext{ NSError *error = nil; NSManagedObjectContext *managedObjectContext = self.managedObjectContext; if (managedObjectContext != nil) { if ([managedObjectContext hasChanges] && ![managedObjectContext save:&error]) { NSLog(@"Unresolved error %@, %@", error, [error userInfo]); abort(); } } } - (NSManagedObjectContext *)managedObjectContext{ if (_managedObjectContext != nil) { return _managedObjectContext; } NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinator]; if (coordinator != nil) { _managedObjectContext = [[NSManagedObjectContext alloc] init]; [_managedObjectContext setPersistentStoreCoordinator:coordinator]; } return _managedObjectContext; } - (NSManagedObjectModel *)managedObjectModel{ if (_managedObjectModel != nil) { return _managedObjectModel; } NSURL *modelURL = [[NSBundle mainBundle] URLForResource:@"NAMEOFYOURMODELHERE" withExtension:@"momd"]; _managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:modelURL]; return _managedObjectModel; } - (NSPersistentStoreCoordinator *)persistentStoreCoordinator { if (_persistentStoreCoordinator != nil) { return _persistentStoreCoordinator; } NSURL *storeURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:@"NAMEOFYOURMODELHERE.sqlite"]; NSError *error = nil; _persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]]; if (![_persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:nil error:&error]) { NSLog(@"Unresolved error %@, %@", error, [error userInfo]); abort(); } return _persistentStoreCoordinator; } #pragma mark - Application's Documents directory // Returns the URL to the application's Documents directory. - (NSURL *)applicationDocumentsDirectory{ return [[[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask] lastObject]; } 

第4步：将数据对象获取到需要数据的ViewControllers

选项1.使用VC中的App Delegate的ManagedObjectContext（首选和更简单）

正如@ brass-kazoo所建议的那样 – 通过以下方式检索对AppDelegate及其managedObjectContext的引用：

迅速

  let appDelegate = UIApplication.sharedApplication().delegate as! AppDelegate appDelegate.managedObjectContext 

目标C.

  [[[UIApplication sharedApplication] delegate] managedObjectContext]; 

在您的ViewController中

选项2.在VC中创建ManagedObjectContext并使其与AppDelegate（原始）中的AppDelegate匹配

仅显示Objective C的旧版本，因为更容易使用首选方法

在ViewController.h中

 @property (nonatomic, retain) NSManagedObjectContext *managedObjectContext; 

在ViewController.m中

 @synthesize managedObjectContext = _managedObjectContext; 

在AppDelegate或创建ViewController的类中，将managedObjectContext设置为与AppDelegate相同

 ViewController.managedObjectContext = self.managedObjectContext; 

如果你想使用Core Data的viewcontroller是一个FetchedResultsController，那么你需要确保这些东西在你的ViewController.h中

 @interface ViewController : UIViewController  { NSFetchedResultsController *fetchedResultsController; NSManagedObjectContext *managedObjectContext; } @property (nonatomic, retain) NSFetchedResultsController *fetchedResultsController; 

这是在ViewController.m中

 @synthesize fetchedResultsController, managedObjectContext; 

完成所有这些后，您现在可以使用此managedObjectContext来运行CoreData良好所需的所有常用fetchRequests！ 请享用

Answer 3

尝试创建Core Data支持的Cocoa应用程序并查看AppDelegate。 您将看到核心数据堆栈实现方法以及用于定义实体和其他核心数据相关内容的托管对象模型文件。

您只向我们展示了头文件（即声明），但没有向我们展示核心数据堆栈的实现（即定义）。

Answer 4

对于Swift 3：包括保存和检索数据

第1步 ：添加框架

第2步：添加数据模型

文件>新建>文件>核心数据>数据模型

• 将文件命名为SampleData ，结果文件将为SampleData.xcdatamocelId

步骤3：将以下function添加到App Delegate，并将“import CoreData”添加到顶部

 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 persistentContainer: NSPersistentContainer = { /* The persistent container for the application. This implementation creates and returns a container, having loaded 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. */ // SEE BELOW LINE OF CODE WHERE THE 'name' IS SET AS THE FILE NAME (SampleData) FOR THE CONTAINER let container = NSPersistentContainer(name: "SampleData") container.loadPersistentStores(completionHandler: { (storeDescription, error) in if let error = error as NSError? { // Replace this implementation with code to handle the error appropriately. // fatalError() 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. /* Typical reasons for an error here include: * The parent directory does not exist, cannot be created, or disallows writing. * The persistent store is not accessible, due to permissions or data protection when the device is locked. * The device is out of space. * The store could not be migrated to the current model version. Check the error message to determine what the actual problem was. */ fatalError("Unresolved error \(error), \(error.userInfo)") } }) return container }() // MARK: - Core Data Saving support func saveContext () { let context = persistentContainer.viewContext if context.hasChanges { do { try context.save() } catch { // Replace this implementation with code to handle the error appropriately. // fatalError() 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. let nserror = error as NSError fatalError("Unresolved error \(nserror), \(nserror.userInfo)") } } } 

第4步：向模型添加实体和属性

a）添加实体

b）添加属性

第5步：保存数据

 func saveItem(itemToSave: String){ let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext //**Note:** Here we are providing the entityName **`Entity`** that we have added in the model let entity = NSEntityDescription.entity(forEntityName: "Entity", in: context) let myItem = NSManagedObject(entity: entity!, insertInto: context) myItem.setValue(itemToSave, forKey: "item") do { try context.save() } catch{ print("There was an error in saving data") } } 

第5步：检索数据

 override func viewWillAppear(_ animated: Bool) { // Obtaining data from model let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext let fetchRequest = NSFetchRequest(entityName: "Entity") do { let results = try context.fetch(fetchRequest) let obtainedResults = results as! [NSManagedObject] let firstResult = obtainedResults[0] let myValue = firstResult.value(forKey: "item") print("myValue: \(myValue)") } catch { print("Error") } } 

Answer 5

如果你在xcode 4中遇到同样的问题，就像我一样。 它是不同的：我必须选择项目，然后在目标中展开“Link Binary With Libraries” ，它显示了当前的库。 从那里单击+（加号）以选择您需要的任何其他库。 我把它放在项目的顶部，不得不将它（拖放）移动到框架组 ，但就是这样。

Answer 6

正如Eimantas所说，你错过了核心堆栈的实现，就像

 - (NSManagedObjectContext *) managedObjectContext; - (NSManagedObjectModel *)managedObjectMode; - (NSPersistentStoreCoordinator *)persistentStoreCoordinator; 

解决方案是创建一个新的核心数据驱动程序项目，并将实现复制/粘贴到您的项目中。

Answer 7

对于Swift 3：

File-> new file-> CoreData-> Model来创建模型。

有关如何实现它的更多信息，请参阅此链接 。

Answer 8

//在Swift 2.2中，您可以在不更改AppDelegate文件的情况下执行以下操作。

1. 项目 – >目标 – >链接框架和库现在添加一个新框架（点击+）’CoreData’
2. File-> new file-> CoreData-> DataModel将其命名为A.xcdatamodelid
3. 在A.xcdatamodelid中创建新的enitity（单击实体+）将其命名为Bc，并在右侧的检查器窗口中将其类设置为“Bc”。
4. 现在向实体添加属性（单击属性+），为例如：name添加一个属性，将其类型添加为String。
5. 现在编辑 – >创建NSManagedObject子类 – >在弹出窗口中单击下一步 – >再次单击 – >然后单击创建。 将创建两个新文件1.一个名为Bc.swift的新类和一个名为Bc + coredataproperties.swift的扩展名。

6. 文件 – >新文件 – > ios-> cocoa触摸类 – >将其子类设置为NSObject->将其命名为DataController.swift文件内包含///

   import UIKit import CoreData类DataController：NSObject {

    var managedObjectContext: NSManagedObjectContext override init() { // This resource is the same name as your xcdatamodeld contained in your project. guard let modelURL = NSBundle.mainBundle().URLForResource("A", withExtension:"momd") else { fatalError("Error loading model from bundle") } // The managed object model for the application. It is a fatal error for the application not to be able to find and load its model. guard let mom = NSManagedObjectModel(contentsOfURL: modelURL) else { fatalError("Error initializing mom from: \(modelURL)") } let psc = NSPersistentStoreCoordinator(managedObjectModel: mom) self.managedObjectContext = NSManagedObjectContext(concurrencyType: .MainQueueConcurrencyType) self.managedObjectContext.persistentStoreCoordinator = psc let urls = NSFileManager.defaultManager().URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask) let docURL = urls[urls.endIndex-1] /* The directory the application uses to store the Core Data store file. This code uses a file named "A.sqlite" in the application's documents directory. */ let storeURL = docURL.URLByAppendingPathComponent("A.sqlite") do { try psc.addPersistentStoreWithType(NSSQLiteStoreType, configuration: nil, URL: storeURL, options: nil) } catch { fatalError("Error migrating store: \(error)") } } 

   }

//////

7. 现在在viewcontroller文件中，您可以使用两种方法访问数据库。 重要说明：在viewController“import CoreData”中包含该语句a。 调用seed（） – >将值插入db / entity b。 call fetch（） – >从db / entity获取值

///////种子（） – > DEF

 func seedPerson() { // create an instance of our managedObjectContext let moc = DataController().managedObjectContext // we set up our entity by selecting the entity and context that we're targeting let entity = NSEntityDescription.insertNewObjectForEntityForName("Bc", inManagedObjectContext: moc) as! Bc // add our data entity.setValue("Meera", forKey: "name") // we save our entity do { try moc.save() } catch { fatalError("Failure to save context: \(error)") } } 

// fetch（）def

 func fetch() { let moc = DataController().managedObjectContext let personFetch = NSFetchRequest(entityName: "Bc") do { let fetchedPerson = try moc.executeFetchRequest(personFetch) as! [Bc] print(fetchedPerson.first!.name!) } catch { fatalError("Failed to fetch person: \(error)") } } 

Answer 9

view.h

  #import  #import  @interface ViewController : UIViewController @property (weak, nonatomic) IBOutlet UITableView *coreDataList; - (IBAction)addBtnClick:(id)sender; @property (strong, nonatomic) NSMutableArray *dataList; @end 

detail.h

  #import  #import  @interface DetailViewController : UIViewController @property (weak, nonatomic) IBOutlet UITextField *nameTxt; @property (weak, nonatomic) IBOutlet UITextField *mobileTxt; @property (weak, nonatomic) IBOutlet UITextField *emailIdTxt; - (IBAction)saveBtnClick:(id)sender; @property (strong,nonatomic) NSManagedObject *userData; @end 

Answer 10

  - (void)viewDidLoad { [super viewDidLoad]; // Do any additional setup after loading the view. if (self.userData) { [self.nameTxt setText:[self.userData valueForKey:@"name"]]; [self.mobileTxt setText:[self.userData valueForKey:@"mobileNumber"]]; [self.emailIdTxt setText:[self.userData valueForKey:@"email"]]; [self.imgView setImage:[UIImage imageWithData:[self.userData valueForKey:@"imageView"]]]; } } - (void)didReceiveMemoryWarning { [super didReceiveMemoryWarning]; // Dispose of any resources that can be recreated. } - (BOOL)textFieldShouldReturn:(UITextField *)textField { [textField resignFirstResponder]; return YES; } /* #pragma mark - Navigation - (IBAction)browseBtn:(id)sender { UIImagePickerController *imgpic =[[UIImagePickerController alloc]init]; imgpic .delegate =self; imgpic .sourceType =UIImagePickerControllerSourceTypePhotoLibrary; [self presentViewController:imgpic animated:YES completion:nil]; } -(void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info { UIImage *choose = info[UIImagePickerControllerOriginalImage]; self.imgView.image=choose; [picker dismissViewControllerAnimated:YES completion:nil]; } - (IBAction)saveBtnClick:(id)sender { NSManagedObjectContext *context = [self managedObjectContext]; if (self.userData) { // Update existing data [self.userData setValue:self.nameTxt.text forKey:@"name"]; [self.userData setValue:self.mobileTxt.text forKey:@"mobileNumber"]; [self.userData setValue:self.emailIdTxt.text forKey:@"email"]; UIImage *sampleimage = _imgView.image; NSData *dataImage = UIImageJPEGRepresentation(sampleimage, 1.0); [self.userData setValue:dataImage forKey:@"imageView"]; } else { // Create a new data NSManagedObject *newDevice = [NSEntityDescription insertNewObjectForEntityForName:@"Details" inManagedObjectContext:context]; [newDevice setValue:self.nameTxt.text forKey:@"name"]; [newDevice setValue:self.mobileTxt.text forKey:@"mobileNumber"]; [newDevice setValue:self.emailIdTxt.text forKey:@"email"]; UIImage *sampleimage = _imgView.image; NSData *dataImage = UIImageJPEGRepresentation(sampleimage, 1.0); [newDevice setValue:dataImage forKey:@"imageView"]; } NSError *error = nil; // Save the object to persistent store if (![context save:&error]) { NSLog(@"Can't Save! %@ %@", error, [error localizedDescription]); } [self dismissViewControllerAnimated:YES completion:nil]; } @end 

。H

  #import  #import  @interface DetailViewController : UIViewController @property (weak, nonatomic) IBOutlet UITextField *nameTxt; @property (weak, nonatomic) IBOutlet UITextField *mobileTxt; @property (weak, nonatomic) IBOutlet UITextField *emailIdTxt; @property (weak, nonatomic) IBOutlet UIImageView *imgView; - (IBAction)browseBtn:(id)sender; - (IBAction)saveBtnClick:(id)sender; @property (strong,nonatomic) NSManagedObject *userData; @end 

Answer 11

  let alert = UIAlertController(title:"Error", message: "No Internet Connection", preferredStyle: .alert) alert.addAction(UIAlertAction(title: "Ok", style: .default, handler: { (action) in})) alert.addAction(UIAlertAction(title: "Try Again", style: .default, handler: { (action) in self.networkCall(text: self.daySelected) })) self.present(alert, animated: false, completion: nil) 

Answer 12

 +(void) insetPlusUpdate:(NSDictionary *)dataa { NSManagedObjectContext * context; if (![[NSThread currentThread] isMainThread]) { context = [[NSManagedObjectContext alloc] init]; [context setPersistentStoreCoordinator:[APP_DELEGATE persistentStoreCoordinator]]; } else { context = [APP_DELEGATE managedObjectContext]; } NSFetchRequest * request = [[NSFetchRequest alloc] init]; NSEntityDescription * entity = [NSEntityDescription entityForName:@"EntityName" inManagedObjectContext:context]; [request setEntity:entity]; NSPredicate * check = [NSPredicate predicateWithFormat:@"attribute == %@", Dict[@"key"]]; [request setPredicate:check]; NSError * error = nil; if ([context countForFetchRequest:request error:&error] == 0) { Entity.attribute = @""; } else { NSArray * array = [context executeFetchRequest:request error:&error]; EntityName * entity = [array firstObject]; Entity.attribute = @""; } } +(NSString *)fetch:(NSString *)feed_id{ NSManagedObjectContext * context; if(![[NSThread currentThread] isMainThread]){ context = [[NSManagedObjectContext alloc] init]; [context setPersistentStoreCoordinator:[APP_DELEGATE persistentStoreCoordinator]]; } else { context = [APP_DELEGATE managedObjectContext]; } NSFetchRequest * request = [[NSFetchRequest alloc] init]; NSEntityDescription * entity = [NSEntityDescription entityForName:@"ENTITYNAME" inManagedObjectContext:context]; [request setEntity:entity]; NSPredicate * check = [NSPredicate predicateWithFormat:@"attribute == %@", Dict[@"key"]]; [request setPredicate:check]; NSError * error = nil; if ([context countForFetchRequest:request error:&error] > 0) { NSArray * array = [context executeFetchRequest:request error:&error]; ENTITYNAME * fetchData = [array firstObject]; NSString * string = fetchData.attribte[@"key"]; return string; } return nil; } +(BOOL)delete{ NSManagedObjectContext * context; if (![[NSThread currentThread] isMainThread]) { context = [[NSManagedObjectContext alloc] init]; [context setPersistentStoreCoordinator:[APP_DELEGATE persistentStoreCoordinator]]; } else { context = [APP_DELEGATE managedObjectContext]; } NSFetchRequest * request = [[NSFetchRequest alloc] init]; NSEntityDescription * entity = [NSEntityDescription entityForName:@"ENTITYNAME" inManagedObjectContext:context]; [request setEntity:entity]; NSError *error = nil; NSBatchDeleteRequest *deleteRequest = [[NSBatchDeleteRequest alloc] initWithFetchRequest: request]; @try{ [context executeRequest:deleteRequest error:&error]; if([context save:&error]){ NSLog(@"Deleted"); return [context save:&error]; } else{ return [context save:&error]; } } @catch(NSException *exception){ NSLog(@"failed %@",exception); return [context save:&error]; } } 

Answer 13

样本编码视图1

 #import "ViewController.h" #import "DetailViewController.h" @interface ViewController () { NSInteger indexPathvalue; } @end @implementation ViewController - (NSManagedObjectContext *)managedObjectContext { NSManagedObjectContext *context = nil; id delegate = [[UIApplication sharedApplication] delegate]; if ([delegate performSelector:@selector(managedObjectContext)]) { context = [delegate managedObjectContext]; } return context; } - (void)viewDidLoad { [super viewDidLoad]; // Do any additional setup after loading the view, typically from a nib. NSLog(@"call this one2"); } - (void)viewDidAppear:(BOOL)animated { [super viewDidAppear:animated]; NSManagedObjectContext *managedObjectContext = [self managedObjectContext]; NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] initWithEntityName:@"Details"]; self.dataList = [[managedObjectContext executeFetchRequest:fetchRequest error:nil] mutableCopy]; [_coreDataList reloadData]; NSLog(@"call this one"); } #pragma mark - Table view data source - (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView { return 1; } - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection: (NSInteger)section { return self.dataList.count; } - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { static NSString *CellIdentifier = @"Cell"; UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier]; if (cell == nil) { cell = [[UITableViewCell alloc]initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier]; } NSManagedObject *user = [self.dataList objectAtIndex:indexPath.row]; cell.textLabel.text = [user valueForKey:@"name"]; cell.detailTextLabel.text = [user valueForKey:@"mobileNumber"]; cell.imageView.image = [UIImage imageWithData:[user valueForKey:@"imageView"]]; return cell; } - (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath: (NSIndexPath *)indexPath { indexPathvalue = indexPath.row; [self performSegueWithIdentifier:@"detailView" sender:self]; } - (BOOL)tableView:(UITableView *)tableView canEditRowAtIndexPath: (NSIndexPath *)indexPath { return YES; } - (void)tableView:(UITableView *)tableView commitEditingStyle: (UITableViewCellEditingStyle)editingStyle forRowAtIndexPath: (NSIndexPath *)indexPath { NSManagedObjectContext *context = [self managedObjectContext]; if (editingStyle == UITableViewCellEditingStyleDelete) { [context deleteObject:[self.dataList objectAtIndex:indexPath.row]]; NSError *error = nil; if (![context save:&error]) { NSLog(@"Can't Delete! %@ %@", error, [error localizedDescription]); return; } [self.dataList removeObjectAtIndex:indexPath.row]; [_coreDataList reloadData]; } } - (void)didReceiveMemoryWarning { [super didReceiveMemoryWarning]; // Dispose of any resources that can be recreated. } - (IBAction)addBtnClick:(id)sender { } #pragma mark - Navigation // In a storyboard-based application, you will often want to do a little - (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender { // Get the new view controller using [segue destinationViewController]. // Pass the selected object to the new view controller. if ([segue.identifier isEqualToString:@"detailView"]) { NSManagedObject *obj = [self.dataList objectAtIndex:indexPathvalue]; DetailViewController *detail = segue.destinationViewController; detail.userData = obj; } } @end 

样本细节视图

  #import "DetailViewController.h" @interface DetailViewController () @end @implementation DetailViewController - (NSManagedObjectContext *)managedObjectContext { NSManagedObjectContext *context = nil; id delegate = [[UIApplication sharedApplication] delegate]; if ([delegate performSelector:@selector(managedObjectContext)]) { context = [delegate managedObjectContext]; } return context; } - (void)viewDidLoad { [super viewDidLoad]; // Do any additional setup after loading the view. if (self.userData) { [self.nameTxt setText:[self.userData valueForKey:@"name"]]; [self.mobileTxt setText:[self.userData valueForKey:@"mobileNumber"]]; [self.emailIdTxt setText:[self.userData valueForKey:@"email"]]; } } - (void)didReceiveMemoryWarning { [super didReceiveMemoryWarning]; // Dispose of any resources that can be recreated. } - (BOOL)textFieldShouldReturn:(UITextField *)textField { [textField resignFirstResponder]; return YES; } /* 

savebutton

  - (IBAction)saveBtnClick:(id)sender { NSManagedObjectContext *context = [self managedObjectContext]; if (self.userData) { // Update existing data [self.userData setValue:self.nameTxt.text forKey:@"name"]; [self.userData setValue:self.mobileTxt.text forKey:@"mobileNumber"]; [self.userData setValue:self.emailIdTxt.text forKey:@"email"]; UIImage *sampleimage = [UIImage imageNamed:@"icon.png"]; NSData *dataImage = UIImageJPEGRepresentation(sampleimage, 1.0); [self.userData setValue:dataImage forKey:@"imageView"]; } else { // Create a new data NSManagedObject *newDevice = [NSEntityDescription insertNewObjectForEntityForName:@"Details" inManagedObjectContext:context]; [newDevice setValue:self.nameTxt.text forKey:@"name"]; [newDevice setValue:self.mobileTxt.text forKey:@"mobileNumber"]; [newDevice setValue:self.emailIdTxt.text forKey:@"email"]; UIImage *sampleimage = [UIImage imageNamed:@"icon.png"]; NSData *dataImage = UIImageJPEGRepresentation(sampleimage, 1.0); [newDevice setValue:dataImage forKey:@"imageView"]; } NSError *error = nil; // Save the object to persistent store if (![context save:&error]) { NSLog(@"Can't Save! %@ %@", error, [error localizedDescription]); } [self dismissViewControllerAnimated:YES completion:nil]; } @end