Stepstepstep

Rails before_filters don't take it far enough. What stepstepstep allows you to do is define before_filters's dependecies in the same way you do with rake tasks.

Stick this in your Gemfile.

gem 'stepstepstep'

class FooController < ApplicationController
  include Stepstepstep

  step :two => [:one_point_three, :one_point_seven] do
    @a << 2
  end
  step :one_point_three => :one do
    @a << 1.3
  end
  step :one do
    @a = [1]
  end
  step :one_point_seven => :one_point_three, :only => :index do
    @a << 1.7
  end

  def index
    render :inline => @a.inspect # => [1, 1.3, 1.7, 2].inspect
  end

  def another
    render :inline => @a.inspect # => [1, 1.3, 2].inspect
  end
end

A few months ago, I was writing a single page application about learning mobile development technology at http://learn.eoe.cn. This page contains lessons, a video, classes, teachers, students, reference material, question-to-answers, exams, chat messages, and their current all learning statuses and dependencies. In brief, there are fifteen steps to load this page, including privileges to judge, fourteen illegal redirect_to , etc. So I need to write a step dependencies management tool, like rake tasks.

At first, I thought maybe I could define several procs in a single before_filter, but the execution context is really complicated. Then one day, I found action_jackson.gem, which was written by Blake Taylor two years ago. The core implementation of this gem is to define each action as a method, and at last call a class method register_filters to register all these methods as before_filter independently. Of course, they're ordered by the earlier declarations. This implementation is not elegant, but the idea is really awesome, it doesn't break Rails's rules.

Then I got a deep understanding of the Rails controllers filters's implementation mechanism. Maybe skip_before_filter helped. In each step, I insert it first, extract all the inserted steps by skip_before_filter, then sort them by TSort(a topological sorting algorithm provided by Ruby standard library), and at last append them again to before_filters. It works, and all rspecs are passed.

I renamed it from action_jackson to stepstepstep, because the DSL is only a step class method, which handles all the details. Most of the implementations were rewritten, and I added rspecs . Thanks Blake Taylor :)