Question

When declaring variables in an interface what is the difference between the two:

@interface thing:NSObject {
    int x;
    int y;
}
@property int x, y;

2:

@interface thing:NSObject {
    @public
    int x;
    int y;
}

Answer 1

@public is an access modifier that means you can access an attribute directly like this:

obj->someAttrib;

@property means that compiler should create accessor methods (if you’re using @synthesize).

An important thing is that property doesn’t necessarily match an attribute. You can create smth like this:

@property(readonly) int doSmth;

and then implement it:

-(int) doSmth {
   return 123+456;
}

However this is very rough and incomplete explanation (there is much more under properties). Read some articles/books about ObjC.