When you inherit difficult code it can take weeks to become productive. I’d like to show you the difference it can make when you have the right tools for the job and know how to use them.
Once you’ve got the code cleaned up to the point where you can see the parts of the logic that belong together, you can start to create a better class structure. A classic refactoring for this is ‘Replace Conditional with Polymorphism’ which was first described in Martin Fowler’s book ‘Refactoring’.
The basic idea is that you create subclasses to encapsulate the logic concerned with each logical case. Your design becomes much more flexible if you need to add new types that are variations on types that are already there - as in this case.
This is the third screencast in the series. My aim is to show that with the right tools and refactoring know-how you can quickly become productive with this code, even without fully understanding the byzantine business rules.