dry_class.rb

### In file version

klass = Class.new do
  def hi
    puts 'hello'
  end
end

name = __FILE__.slice(/\w*.rb$/).slice(/\w*/).camelcase
Object.const_set(name, klass)

### Extracted version

class Dryer
  def self.dry_class(file_name, &blk)
    klass = Class.new &blk
    name = __FILE__.slice(/\w*.rb$/).slice(/\w*/).camelcase
    Object.const_set(name, klass)
  end
end

Dryer.dry_class(__FILE__) do
  def herp
    puts 'hello'
  end
end

### with inheritance

class Dryer
  def self.dry_class(file_name, super_class, &blk)
    klass = Class.new(super_class, &blk)
    name = __FILE__.slice(/\w*.rb$/).slice(/\w*/).camelcase
    Object.const_set(name, klass)
  end
end

Dryer.dry_class(__FILE__, ActiveRecord::Base) do
  def herp
    puts 'hello'
  end
end

latest crazy rails version:

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

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

      if const.const_defined?(next_const)
        const.const_get(next_const)
      else
        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
  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
    self.class.all_autoload_paths.map{|p| file_path[/^#{p}/] || ""}.sort.last + '/'
  end

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