I haven't used abstract classes much in practice, though I understand what they are : a way to dictate to subclasses which methods must be implemented.
I just put a Kohana project through Doxygen and can see the class hierarchy in its entirety. I see that, at the top of the chain we have a factory:
abstract class Kohana_Model {
public static function factory($name){
// Add the model prefix
$class = 'Model_'.$name;
return new $class;
}
}
Inherited directly below that, we have an empty abstract class:
abstract class Model extends Kohana_Model {}
... And below that, there are three inherited classes: Kohana_Model_Database, Kohana_ORM, and Model_Foobar.
Would someone please explain the programming reasoning for this - what is the purpose of having an empty abstract class this high up in the chain? (and, at all?)
Why not have Kohana_Model_Database, Kohana_ORM, and Model_Foobar inherit directly from Kohana_Model, when there is (apparently?) no other branching or inheritance going on between Model and Kohana_Model?
