How to implement multiple inheritance in delphi?

Question

I'm doing a full rewrite of an old library, and I'm not sure how to handle this situation (for the sake of being understood, all hail the bike analogy):

I have the following classes:

• TBike - the bike itself
• TBikeWheel - one of the bike's wheel
• TBikeWheelFront and TBikeWheelBack, both inherits from TBikeWheel and then implements the specific stuff they need on top of it

This is pretty straightforward, but now I decide to create multiple kind of bikes, each bikes having it's own kinds of wheel - they do the same stuff as a regular front/back wheels, plus the specific for that bike.

• TBikeXYZ - inherits from TBike
• TBikeWheelXYZ - inherits from TBikeWheel

And here is my problem: TBikeWheelFrontXYZ should inherit from TBikeWheelXYZ (to get the specific methods of an XYZ wheel), but it should also inherit from TBikeWheelFront (to get the specific methods of a front wheel).

My question here is, how can I implement that in a way that doesn't:

1. feel like a hack
2. force me to rewrite the same code several time

Answer 1

Delphi does not support Multiple Inheritance. But classes can support / implement multiple interfaces and you can delegate interface implementation, so you can kinda simulate multiple inheritence.