dryer.rb

=begin
This class allows you to condsolidate the declaration of class names into
the file name. It also handles namespacing based on the file path if you are
using Rails autoloading.

This works with the single exception of constant lookup via nesting, so you
will need to replace constants with variables and methods.

Examples:

# app/models/user.rb

Dryer.def_class(__FILE__) do
  def hi
    "hello world"
  end
end

User.new.hi
=> "hello world"

# app/models/instruments/horn.rb

Dryer.def_class(__FILE__) do
  def play
    "toot!"
  end
end

Instruments::Horn.new.play
=> "toot!"

# app/models/address.rb

Dryer.def_class(__FILE__, ActiveRecord::Base) do
end

Address.new.respond_to? :save
=> true
=end

class Dryer < Struct.new(:file_path, :super_class, :blk)
  def self.def_class(file_path, super_class=Object, &blk)
    new(file_path, super_class, blk).def_class
  end

  def def_class
    constant_names.each.with_index.inject(Object) do |const, (next_const, index)|

      if constant_names.length == index + 1

        # this is needed to set the class name so that activerecord
        # works properly
        klass = const.const_set(next_const, Class.new(super_class))

        # here we eval the class block to define methods and everything
        klass.class_eval &blk
      else
        const.const_get(next_const)
      end
    end
  end

  def constant_names
    get_name.split('/').map(&:camelcase)
  end

  def get_name
    file_path.gsub(most_likely_path, '').gsub(".rb", '')
  end

  def most_likely_path
    all_autoload_paths.map{|p| file_path[/^#{p}/] || ""}.sort.last + '/'
  end

  def all_autoload_paths
    config = Rails.configuration
    config.autoload_paths + config.eager_load_paths + config.autoload_once_paths
  end
end