how do I configure the view for NSNumber when trying to set the value from Core Data

Question

I am building my project using a master detail VC template with core data.

I am trying to set the values for my attributes in the detail window.

When transitioning from the MasterViewController to the FoodDetailViewController, my NSString attribute works perfectly.

When I add code to add the calorie value attribute (set up as integer 16) my app crashes.

I generated a class file for my entity and the calories property is declared like this:

@property (nonatomic, retain) NSNumber * calories;

This is how I set up the transition.

In MasterViewController.m in prepareForSegue, I set the keyString as such:

foodDetailVC.calorieKeyString = @"calories”;

Then in FoodDetailViewController.h I did:

@property (nonatomic, strong) NSString *calorieKeyString;

in FoodDetailViewController.m I did:

-(void)configureView
{
if (self.managedNutritionValuesObject) {
    //refresh content to ensure most up to date data
    [self.managedObjectContext refreshObject:self.managedNutritionValuesObject
                                mergeChanges:YES];

    //covert NSNumber values to NSString values
    NSString *caloriesString = [NSString stringWithFormat:@"%@", 
    self.managedNutritionValuesObject.calories];

//set nutrition values in text fields
    //these first two lines are for food text field
    self.foodNameTextField.text = [self.managedNutritionValuesObject 
    valueForKey:self.foodNameKeyString];
    self.foodNameTextField.clearsOnBeginEditing = YES;
    self.caloriesTextField.text = [caloriesString valueForKey:self.calorieKeyString];
    self.caloriesTextField.text = caloriesString;

 }
}

the crash log says it is crashing on configure view and I get this message:

* Terminating app due to uncaught exception 'NSUnknownKeyException', reason:
'[<__NSCFString 0x8b44e20> valueForUndefinedKey:]: this class is not key value coding-compliant for the key calories.’

Any help would be greatly appreciated, Thanks

Answer 1

self.caloriesTextField.text = [self.managedNutritionValuesObject valueForKey:@"calories"];