Ylan Segal

Sandi Metz' Revised Rules

I previously wrote about Sandi Metz‘ proposed rules. I had the pleasure of hearing her talk about them last week at the monthly SDRuby meeting.

It turns out that she misspoke in the original Ruby Rogues Podcast Episode and has since revised them to be:

  • No More Than:
    • 100 lines per class
    • 5 lines per method
    • 4 (or even better 3) parameters per method (each hash key counts)
    • 1 instance variable per view
    • 2 class names per controller (1 business object, 1 presentation object)

The main difference from the previous rules, as mentioned on the podcast is that each controller can know about 2 class names: This is pretty significant. I have been trying to adhere to the original rules for a long time. However, no matter how hard I tried, I could not get a controller action that just talked to 1 object, because that meant coupling the view to the business object, which just felt wrong. In the end, I just let it be and created a business object, which was later decorated by another object for the view. After hearing Sandi’s revised rules, I feel vindicated!

This reminds me of the dispensation: You can break any of the rules, as long as someone else on the team agrees.

Code draws code like it

Sandi Metz

I really enjoyed hearing Sandi talk. The SDRuby taping is not yet available, but it looks like Sandi gave the same talk elsewhere.