Question

I have a Class with an instance variable of an NSArray of different objects I know should inherit from the same superclass. My question is how do I access the instance variables and methods from another class (its controller) while ensuring that the contents of the array contains only objects that are a subclass of a certain class? I tried implementing a minimal protocol and refencing the objects in the array as type id and (id *) but that won’t let me access any instance variables or methods of the classes in the array (and rightly so).
In object file

NSArray* components; // contains subclasses of component

In the controller file

subclassofClassObject* object; 

is there a subclassOf function, macro, typedef … etc or a workaround so I can reference the subclasses of component in a subclass of object from a subclass of controller. i.e something to replace subclassofClass.

Answer 1

I don’t quite follow what you’re asking, but maybe the following will help:

You can determine if you have an instance of a class, or one of its subclasses using isKindOfClass:. For example given a class MyBaseClass, then use a cast:

id elem = [components objectAtIndex:ix];
if ([elem isKindOfClass:[MyBaseClass class]])
{
   // elem is an instance of MyBaseClass or one of its subclasses so cast is safe
   MyBaseClass *mbc = (MyBaseClass *)elem;
   // now can access methods, properties and public instance variables
   // of MyBaseClass via mbc without warnings
   ...
}