Question

Please can any one tell me whats the difference between declaring a variable inside { } vs outside of @interface & @end in header file. Both ways lead to successful compilation.

Answer 1

if you want the variable to be part of the class (a.k.a. instance variable) then you declare it inside the brackets, otherwise it is declared as a global variable which has nothing to do with the class.

e.g.

// XYZ.h

@interface XYZ
{
  int myinstancevariable;
}
@end

int myglobalvariable;

…

XYZ* a = [[XYZ alloc] init];
NSLog(@"%d", [a myinstancevariable]);
NSLog(@"%d", myglobalvariable );

edit: forgot {}