Wednesday, 1 January 2014

Clean Code. "I do not think that word means what you think it means."

From my copy of Clean Code: A Handbook of Agile Software Craftsmanship (the paper copy of which (barely) predates my work in Rails. The highlighted paragraph is what I'd highlighted in the paper copy:

Active Record

Active Records are special forms of DTOs. They are data structures with public (or bean- accessed) variables; but they typically have navigational methods like save and find. Typically these Active Records are direct translations from database tables, or other data sources.

Unfortunately we often find that developers try to treat these data structures as though they were objects by putting business rule methods in them. This is awkward because it creates a hybrid between a data structure and an object.

The solution, of course, is to treat the Active Record as a data structure and to create separate objects that contain the business rules and that hide their internal data (which are probably just instances of the Active Record).

I've been increasingly uncomfortable with the way Rails encourages people to conflate the domain model objects with persistence in Rails' core component, ActiveRecord. Running across this bit again makes me think of Inigo Montoya from The Princess Bride: You keep using that word. I do not think it means what you think it means. Judging from my own projects and those I've participated in and observed on Github, the fact that ActiveRecord does not properly implement or encourage the Active Record pattern is a primary root cause of many bugs and much confusion and heartburn.

Happy New Year.