Question

this is the code:

NSNumber *taskId = [[self.taskList objectAtIndex:indexPath.row] valueForKey:@"identity"];    
NSInteger *intTaskId = [[self.taskList objectAtIndex:indexPath.row] valueForKey:@"identity"];

self.taskList is an NSArray which filled with core data fetch request in ViewController’s viewDidLoad method.
the taskId is: 1
the intTaskId is: 269303816
In actually, the value stored in core data is: 1

below is my questions:
1, I am confused why the NSInteger incorrect?
2, Should I have to replace NSInteger with NSNumber to avoid any other problems?

Answer 1

NSNumber is an object, whereas NSInteger is simply a typedef for a primitive (non-object) type (like int). NSInteger is not a subclass of NSNumber. Core Data returns numbers as instances of NSNumber. You’re getting the weird NSInteger value because it’s pointing to an object of type NSNumber but attempting to print it as if it were just an integer.

You’ll need to replace NSInteger with NSNumber to avoid any problems. You could also use the intValue method on NSNumber to get back an NSInteger:

NSNumber *objTaskId = [[self.taskList objectAtIndex:indexPath.row] valueForKey:@"identity"];
NSInteger *intTaskId = [objTaskId intValue];

You’ll need to do this if you want to do comparisons (greater than, equal too, smaller than) or arithmetic (you can’t add an NSNumber to another NSNumber or an NSNumber to a primitive type like an int or float).