instance variables in @interface; header vs implementation

Question

Is there any difference between declaring a private instance variable in the header vs declaring it in the implementation?

in TestObj.h

@interface TestOb         


        

Answer 1

Greg Parker's comment on the accepted answer is the best answer here:

There is one functional difference: ivars in the class's @interface are @protected by default, and ivars in a class extension @interface or in @implementation are @private by default.