🚀 go-pugleaf

george@gmsys.com (George Farris) wrote:
>I'm trying to learn Objective-C and am confused about the 
>inheritance of instance variables.  In the following code
>"Parent" has a variable called "name".  "Child" is a subclass
>of "Parent".  From reading information on Obj-C I understood that
>the "Child" would be able to see "name", it doesn't.

<snip>


>@implementation Child
>-init
>{
>        printf("In Child name is ->%s\n", name);
>        return self;
>}
>
>@end

The above code should read -

@implementation Child
-init
{
  [super init];
  printf("In Child name is ->%s\n", name);
  return self;
}
@end

The initialiser for Child must call the initialiser for it's superclass
(in this case Parent).

Objective-C is unlike C++ in this respect -
In C++ the compiler calls constructors and desctructors automatically.
In Objective-C your code calls the 'alloc...', 'init...' and 'dealloc' methods
of the superclass itsself.

This means that in Objective-C, you have a little more work to do, but you gain
considerable flexibility in what you can do in the way of using different
construction/destruction techniques based on runtime decisions.

For the beginner like yourself, this will probably seem like a considerable annoyance -
'why should I have to remember to call [super init] in all my initialisers just to
gain flexibility I'll probably never use' -
Believe me - once you have written a few large projects in Objective-C and C++ you will
bless the extra flexibility of Objective-C.