Switching on an Attribute of Another Object

It is a bad idea to do a switch based on an attribute of another object. If you must, it should be on your own data, not someone else’s. - Refactoring by Martin Fowler

We’re reading Refactoring as part of an internal book club. This quote reminds me of the Feature Envy code smell.

class Cart
  def price
    @item.price + @item.tax
  end
end

If most of the work in a method is being done on another object (@item), the method should be on that other object.

If you haven’t played with Kevin Rutherford’s Reek gem before, it’s a neat way to find smells like Feature Envy in your Ruby code.

About thoughtbot

We've been helping engineering teams deliver exceptional products for over 20 years. Our designers, developers, and product managers work closely with teams to solve your toughest software challenges through collaborative design and development. Learn more about us.