由于未捕获的异常'NSInvalidArgumentException'而终止应用程序，原因：'+ entityForName：nil不是合法的NSManagedObjectContext

Question

I am getting a null result for

AppDelegate.h

@property (readonly, strong, nonatomic) NSManagedObjectContext *managedObjectContext;
@property (readonly, strong, nonatomic) NSManagedObjectModel *managedObjectModel;
@property (readonly, strong, nonatomic) NSPersistentStoreCoordinator *persistentStoreCoordinator;

AppDelegate.m

    @synthesize managedObjectContext = __managedObjectContext;
    @synthesize managedObjectModel = __managedObjectModel;
    @synthesize persistentStoreCoordinator = __persistentStoreCoordinator;

    - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
    {
          Person *newPerson = [NSEntityDescription
          insertNewObjectForEntityForName:@"Person"
          inManagedObjectContext:self.managedObjectContext];
          .......

    }

I have one xcdatamodeld file with a entity of Person and a attribute of name. I made a Person.h and .m file from a NSManagedObject.

Why am I getting a null result for my output.

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

Answer 1

In your viewController.m implementation file, right under this bit of code:

- (void)viewDidLoad
{

add this bit of code:

id delegate = [[UIApplication sharedApplication] delegate];
    self.managedObjectContext = [delegate managedObjectContext];

Answer 2

I realized that since I was not adding Core Data when I originally created the project, I was missing some code that is automatically generated when the core data option is ticked. Thus, when I followed some tutorials online, this automatically generated code is assumed. That's where I messed up.

Answer 3

确保在引发异常时运行的代码正在您创建托管对象上下文的同一线程上运行。

Answer 4

如果您使用的是使用NSPersistentContainer的项目模板，请确保在iOS 10+上运行此模板，否则当您执行某种Core Data操作时，它会因初始化而崩溃并崩溃。