No Comments Posted on April 9th, 2008 by Mike Laurence

Rails-Style Dynamic Finders For Ruby Arrays

Category: Capricious Coding, Tags: , ,

One of my favorite little elegances in Ruby on Rails is ActiveRecord’s dynamic finder magic. It lets you perform simple model queries with as much readability as is conceivable in a method call:
# Normal ActiveRecord call - tasty, but still a bit bland.
Sandwich.find(:all, :conditions => ['meat = ? and tastiness = ?', 'turkey', 'medium'])

# Dynamic finder - unequivocally delicious. Try it with chocolate!
Sandwich.find_all_by_meat_and_tastiness('bacon', 'very')
Lost in the wonders of such syntactic saltiness (er, sugariness), I frequently found myself using these kinds of commands on arrays of model objects I had already retrieved from the database. Naturally enough, all I encountered was a variety of colorful exceptions, but I continued to dream of a world where dynamic finders worked for arrays, too.

Fortunately, a little experimentation, a covert glance at the ActiveRecord code, and a timely discovery of the wonders of inject led me to a successful implementation:

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