refined is a technique for chaining scopes (or class methods as it were in rails (see http://elabs.se/blog/24-scopes-are-obsolete/ "Scopes Are Obsolete") to facilitate easy filtering of ActiveRecord collections.

Installation

gem install refined

When used with Rails 3

in a Gemfile:

gem 'refined'

Example Use

Simple collection scoping

This is not a super practical use but one could do:

Candidate.refined({status: "pending", skill: "advanced"})

However that's not much shorter than:

Candidate.where("status = ? OR skill = ?", "pending", "advanced")

A Simple View Filter

Let's say you want to filter a list of candidates for hire by status and skill level. The code might look something like this.

class Candidate < ActiveRecord::Base; end

controller Candidates < ApplicationController
  expose(:candidates) { Candidate.refined(params[:filters]) }

  def filter
    render :index
  end
end

= form_for :filters, url: filter_candidates_url do |f|
  %fieldset
    %dl
      %dt Status
      %dd= f.select :status, ["pending", "hired", "rejected"]

      %dt Skill
      %dd= f.select :skill, ["beginner", "intermediate", "advanced"]
  %fieldset.action
    = f.submit "Filter"

%table
  %thead
    %tr
      - ["Name", "Status", "Skill"].each do |header|
        %th header
  %tbody
    - candidates.each do |candidate|
      %tr
        %td= candidate.name
        %td= candidate.status
        %td= candidate.skill

The call to Candidate.refined(params[:filters]) will yield 2 class methods created on Candidate as such:

def self.status(arg)
  where(status: arg)
end

def self.skill(arg)
  where(skill: arg)
end

And will chain those methods as Candidate.status("pending").skill("advanced") returning the scoped collection of candidates.

TODO

• Rails 2 support
• Ruby 1.8 support
• Multiple parameters
• More AREL finder methods
• Accessor methods for parameter values