核心数据错误：nil不是合法的NSManagedObjectContext参数

Question

我是创建iOS应用程序的新手。我必须快速创建一个表单应用程序，我可以从愿意填写信息的人那里存储信息。基本上只是一堆文本字段，如名称，邮件等。

表单填写完成后，使用这一位代码存储他们的数据：

//Save action 
NSEntityDescription *entityDesc = [NSEntityDescription entityForName:@"Person" inManagedObjectContext: context]; 
NSManagedObject *newPerson = [[NSManagedObject alloc]initWithEntity:entityDesc insertIntoManagedObjectContext:context]; 

//Fill in values 
[newPerson setValue:self.btnPrefix.titleLabel.text forKey: @"prefix"]; 
[newPerson setValue:self.txtFirstName.text forKey: @"firstname"]; 
[newPerson setValue:self.txtLastName.text forKey: @"lastname"]; 
[newPerson setValue:self.txtLive.text forKey: @"country"]; 
[newPerson setValue:self.txtMail.text forKey: @"email"]; 
[newPerson setValue:self.txtPhone.text forKey: @"phonenumber"]; 
[newPerson setValue:self.txtLinked.text forKey: @"linkedIn"]; 
[newPerson setValue:self.txtAbout.text forKey: @"about"]; 

NSError *error; 
[context save:&error]; 

当在模拟器上执行时根本没有问题。但是，一旦在iPad上运行我得到这个错误：

Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '+entityForName: nil is not a legal NSManagedObjectContext parameter searching for entity name 'Person''

调试它就会在第一行triggerd后：

NSEntityDescription *entityDesc = [NSEntityDescription entityForName:@"Person" inManagedObjectContext: context]; 

了些研究后，我的AppDelegate包含零persistentContainer当跑设备，但在虚拟设备上运行时会填充它。所以我想问题在那里，但我找不到解决问题的方法。

- (void)viewDidLoad { 
    [super viewDidLoad]; 
    AppDelegate *appdelegate = (AppDelegate*)[[UIApplication sharedApplication]delegate]; 
    context = appdelegate.persistentContainer.viewContext; 
} 

任何人都可以帮我吗？

Answer 1

对于遇到此错误的人。最有可能的是，如果它在虚拟设备上工作，但不在物理设备上，这是由于iOS 9和10之间访问核心数据的差异造成的。

在Xcode 8中，AppDelegate会自动为iOS 10生成数据，但如果您停留在iOS 9，您需要在您的代理文件中添加以下代码：

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

- (NSURL *) applicationDocumentsDirectory{ 
    return [[[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask] lastObject]; 
} 

- (NSManagedObjectModel *)managedObjectModel { 
    if(_managedObjectModel != nil){ 
     return _managedObjectModel; 
    } 
    NSURL *modelURL = [[NSBundle mainBundle] URLForResource:@"StylelabsForms" withExtension:@"momd"]; 
    _managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:modelURL]; 
    return _managedObjectModel; 
} 

- (NSPersistentStoreCoordinator *) persistentStoreCoordinator{ 
    if(_persistentStoreCoordinator != nil){ 
     return _persistentStoreCoordinator; 
    } 

    _persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]]; 
    NSURL *storeURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:@"StylelabsForms.sqlite"]; 
    NSError *error = nil; 
    NSString *failureReason = @"Error loading saved data"; 
    if(![_persistentStoreCoordinator addPersistentStoreWithType: NSSQLiteStoreType configuration:nil URL: storeURL options:nil error:&error]){ 
     NSMutableDictionary *dict = [NSMutableDictionary dictionary]; 
     dict[NSLocalizedDescriptionKey] = @"Failed init application's saved data"; 
     dict[NSLocalizedFailureReasonErrorKey] = failureReason; 
     dict[NSUnderlyingErrorKey] = error; 
     error = [NSError errorWithDomain:@"YOUR_ERROR_DOMAIN" code:9999 userInfo:dict]; 
     NSLog(@"Unresolved error %@, %@", error, [error userInfo]); 
     abort(); 
    } 

    return _persistentStoreCoordinator; 
} 

- (NSManagedObjectContext *) managedObjectContext { 
    if (_managedObjectContext != nil){ 
     return _managedObjectContext; 
    } 

    NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinator]; 
    if(!coordinator) { 
     return nil; 
    } 
    _managedObjectContext = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSMainQueueConcurrencyType]; 
    [_managedObjectContext setPersistentStoreCoordinator:coordinator]; 

    return _managedObjectContext; 
} 

而且适应保存如下：

- (void)saveContext { 
    NSManagedObjectContext *managedObjectContext = self.managedObjectContext; 
    if(managedObjectContext != nil){ 
     NSError *error = nil; 
     if([managedObjectContext hasChanges] && ![managedObjectContext save:&error]){ 
      NSLog(@"Unresolved error %@, %@", error, [error userInfo]); 
      abort(); 
     } 
    } 

    //For iOS 10 and above 
    /* 
    NSManagedObjectContext *context = self.persistentContainer.viewContext; 
    NSError *error = nil; 
    if ([context hasChanges] && ![context 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(); 
    } */ 
} 

Answer 2

私人懒VAR applicationDocumentsDirectory：URL = {// 目录th e应用程序用于存储Core Data存储文件。此代码使用应用程序的文档Application Support目录中指定的目录。 让网址= FileManager.default.urls（为：.documentDirectory在：.userDomainMask） 回报的网址[urls.count-1] }（）

private 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 = Bundle.main.url(forResource: "CoreData", withExtension: "momd")! 
    return NSManagedObjectModel(contentsOf: modelURL)! 
}() 

private lazy var persistentStoreCoordinator: NSPersistentStoreCoordinator = { 
    // The persistent store coordinator for the application. This implementation creates and returns 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 
    let coordinator = NSPersistentStoreCoordinator(managedObjectModel: self.managedObjectModel) 
    let url = self.applicationDocumentsDirectory.appendingPathComponent("CoreData.sqlite") 
    var failureReason = "There was an error creating or loading the application's saved data." 
    do { 
     // Configure automatic migration. 
     let options = [ NSMigratePersistentStoresAutomaticallyOption : true, NSInferMappingModelAutomaticallyOption : true ] 
     try coordinator.addPersistentStore(ofType: NSSQLiteStoreType, configurationName: nil, at: url, options: options) 
    } catch { 
     // Report any error we got. 
     var dict = [String: AnyObject]() 
     dict[NSLocalizedDescriptionKey] = "Failed to initialize the application's saved data" as AnyObject? 
     dict[NSLocalizedFailureReasonErrorKey] = failureReason as AnyObject? 

     dict[NSUnderlyingErrorKey] = error as NSError 
     let wrappedError = 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 \(wrappedError), \(wrappedError.userInfo)") 
     abort() 
    } 

    return coordinator 
}() 

lazy var managedObjectContext: NSManagedObjectContext = { 

    var managedObjectContext: NSManagedObjectContext? 
    if #available(iOS 10.0, *){ 

     managedObjectContext = self.persistentContainer.viewContext 
    } 
    else{ 
    // 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 
    managedObjectContext = NSManagedObjectContext(concurrencyType: .mainQueueConcurrencyType) 
    managedObjectContext?.persistentStoreCoordinator = coordinator 

    } 
    return managedObjectContext! 
}() 
// iOS-10 
@available(iOS 10.0, *) 
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. 
    */ 
    let container = NSPersistentContainer(name: "CoreData") 
    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)") 
     } 
    }) 
    print("\(self.applicationDocumentsDirectory)") 
    return container 
}()