This post originated from an RSS feed registered with Agile Buzz by Keith Ray. Original Post: Exploring an Extreme of Refactoring Feed Title: MemoRanda Feed URL: http://homepage.mac.com/1/homepage404ErrorPage.html Feed Description: Keith Ray's notes to be remembered on agile software development, project management, oo programming, and other topics. Latest Agile Buzz Posts Latest Agile Buzz Posts by Keith Ray Latest Posts From MemoRanda

Kent Beck once wrote of the Three Bears [Pedagogical] Pattern (scroll down to pattern #17): to enable a student to learn about something by exploring its limits. Quoting Kent: I have taught requirements engineering with this technique. I ask the learners to write stories that will define the system—too large in scope to be useful, one too small, and one just right. I taught this technique in India and ended up telling the story of Goldilocks and the Three Bears after lunch.

Brian Button decided to explore refactoring by taking the Video Store example from Martin Fowler's book and refactoring it into methods one line long, no private methods, and aggressively removing all duplication, particularly duplication of iteration over containers.

His starting point (and Fowler's ending point) is the class named "Customer", containing a list of rentals. It has private methods for calculating rental cost and "frequent renter points", and a large method for printing the customer's statement. Brian's ending point is seven classes: Customer, RentalStatement, RentalCollection, Collector, LineItemPrinter, FrequentPointsTotaller, RentalCostTotaller.

If he had been programming in Ruby or Smalltalk instead of C#, he probably could have met his goals with only first two classes. Blocks and iteration methods built into Smalltalk/Ruby collection classes would have eliminated the need to create the other five classes. Brian wrote:

Now for the questions. Is this code more clear than the original Customer class? I’m not sure. In some senses it is. If I want to go see how the statement is generated, I can now go look at a RentalStatement class and see it. Looking ahead a bit, knowing that one of the changes Martin talks about in his book is that we need to support an HTML statement as well as a text statement, so by creating the RentalStatement class, we’re well prepared to make that change. I’m never sure if the ReplaceExternalIterationWithInternalIteration ever makes code more clear, but it does eliminate duplication.

I’m not sure that I would ever go this far in real life, but it is nice to know that I could.