AppDelegate.h

@property (readonly,strong,nonatomic) NSManagedObjectContext *managedObjectContext;
@property (readonly,nonatomic) NSManagedObjectModel *managedObjectModel;
@property (readonly,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];
          .......

    }

我有一个xcdatamodeld文件,其实体为Person,属性为name.我从NSManagedObject创建了一个Person.h和.m文件.

为什么我的输出结果为null.

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