Objective-C private instance variables definition

Question

Is there any difference in where we define private instance variables? As I understand there are two possibilties:

1) In header file

@interface MyViewController : UIViewController {
    @private
    NSString *fooString;
}

2) Second way is to define it in the implementation:

@implementation MyViewController
NSString *fooString;

What is the difference? Cheers!

Answer 1

In 2nd case fooString is not instance variable - it is global variable, so your two cases are completely different