I see over-reliance on inheritance as one of the major pitfalls of OO design

Personally, I think that a better more general was to say that is, "The mis-use of inheritance is one of the major pitfalls of OO Design". Over-reliance is only one of the problems out there, under-reliance can be just as bad (when people don't understand when to use it, rather then just not knowing when not to use it).

I agree with a lot of what you are saying, there is far to much inheritance shoehorning going on these days (although that is not really what simonm is doing, you might want to look closer at the implementation in Text::MicroMason (make sure you are looking at the latest developer release)). I have always felt that inheritance is best when it is employed in seperate clusters of shallow heirarchies which (usually) are not related to one another (a.k.a. highly decoupled).

... I can go on further, but in case this doesn't make sense I'll wait and see if anyone understands what I've just said.

What you just described is actually an excellent case for a specific style of inheritance. Interface Polymorphism is IMO of the great underused and misunderstood aspects of OO programming.

To do what you describe (have a MetaThing which takes an array of Things and "runs" each of them in turn) it is usually a good idea to have a common base which all Things are derived from. If for no other reason then for MetaThing to be able to indentify each Thing as a Thing. The knee-jerk approach is to make Thing::Base and have all Things inherit from it. However, this approach limits you in several ways since all your Things must inherit from Thing::Base.

However, a better solution to this all is to create a Thing interface. Then all MetaThing needs to know is that your Thing conforms to the Thing interface, everything else is irrelvant to MetaThing. The idea really is that you try not to program "to the class", but instead "program to the interface". I have found that thinking this way tends to lead to highly reusable code and very clean designs.

-stvn

In reply to Re^2: Solving the SUPER problem in Mixins with String Eval by stvn
in thread Solving the SUPER problem in Mixins with String Eval by simonm

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