I constantly hear about inheritance being a prime factor in determining if something is OO or not, and how useful it is for OO programming.

To some extent, inheritance is overemphasised by some people when talking about OO development. Not that it's completely useless, but you often find it used where options like delegation would be a better design choice.

So my question is, when/what have you actually used inheritance (for) in a 'real' project? Real in this case meaning a project not done solely for experimentation purposes

Some of my recent (real world) uses of inheritance have included:

• Subclassing various CGI::Kwiki modules to provide some specialised formatting and behaviour.
• Creating a memory-caching subclass of an object-relational persistance class.
• Refactoring some common behaviour from several Test::Class classes into a common super-class.

Basically, places where you want to specialise behaviour.