Session 5

Pair Programming and Refactoring

Agile Software Development

Ruby Theme: Gems

... package system. Install, then use to bring in external packages to use.

... example: Reek, a smell detector. Install:

    macbook >sudo gem install reek

    Thank you for downloading Reek. For info:
      - see the reek wiki
      - follow @rubyreek on twitter
    Successfully installed sexp_processor-3.0.4
    Successfully installed ruby_parser-2.0.4
    Successfully installed ruby2ruby-1.2.4
    Successfully installed reek-1.2.8
    4 gems installed
    Installing ri documentation for [all four]
    Installing RDoc documentation for [all four]

Now we can run reek against any Ruby file for feedback on code style and design. [] comments are mine.

    macbook > reek Customer.rb 
    Customer.rb -- 12 warnings:
      Customer has no descriptive comment (IrresponsibleModule)
      Customer#addRental has the name 'addRental' (UncommunicativeName)
      Customer#getName has the name 'getName' (UncommunicativeName)
      Customer#statement calls (frequentRenterPoints + 1) twice (Duplication)
[move the computation to a helper method]
      Customer#statement calls entry.getDaysRented 6 times (Duplication)
      Customer#statement calls entry.getMovie 3 times (Duplication)
      Customer#statement calls entry.getMovie.getPriceCode twice (Duplication)
[move the computation to the receiver class]
      Customer#statement has approx 17 statements (LongMethod)
[extract helper methods]
      Customer#statement has the variable name 'frequentRenterPoints' (UncommunicativeName)
      Customer#statement has the variable name 'thisAmount' (UncommunicativeName)
      Customer#statement has the variable name 'totalAmount' (UncommunicativeName)
      Customer#statement refers to entry more than self (LowCohesion)

RubyGems is the standard packaging and distribution system used in the Ruby community.

Refactoring Support in an IDE

... we looked at RubyMine, a relatively new Ruby IDE that offers support for a few common refactorings.

We used RubyMine to refactor the movie store codebase we worked on last time, adapted from Fowler's refactoring book. In particular, we

This is similar to the set of refactorings Fowler himself applies to this code in Chapter 1 of his book!

We ran our tests as often as we could throughout the process, to ensure that we weren't breaking the code or changing its behavior. The resulting code is available as a zip file.

Preparing for the Project

Over the next three weeks. we will grow the beginnings of a small accounting system. Here are some of the ideas that will be part of a complete system:

Next time, we will write up stories for this system and play the Planning Game to decide what you will work on for our one release (end of the course) and our three iterations (end of each week).

Most of the significant stories will be written at the beginning of the project and divided into "must have", "nice to have", and "won't have" piles. We will draw up a tentative list of stories for the first iteration, and a less certain list of stories for the remaining iterations. As your customer, I will try to ensure a certain coherence among the priorities I set for the stories. I'll make tradeoffs among the priorities based on feedback of various kinds, including your work each iteration.

As the project goes on, we may add new stories, but in general we expect the number of stories under consideration to trend toward zero.

Project Details

... communication via wiki and mailing list.

... version control via Subversion, github, or Mercurial.

... common team standards and tools. A common IDE or editor? A common programming style?

Wrap Up

Eugene Wallingford ..... ..... May 17, 2010