Duplicating Rails model for a form with meta-programming

Can someone please review my code:

# dup/ish -> //github.com/rails/rails/issues/5449

class Form
  include Mongoid::Document

  attr_accessor :source

  def self.ish(prefix, suffix, &block)
    klass_name = prefix.classify + suffix

    dup.tap do |klass|
      klass.class_eval do
        define_singleton_method(:name) do
          prefix.classify
        end
      end

      klass.class_eval(&block)

      Object.const_set(klass_name, klass)
    end
  end

  def self.compose(klass_name, id, source)

    mongoid_translate = {:models => {}, :attributes => {}}

    form = ish(klass_name, id) do

      translate = {}

      source.flatten.each do |widget|
        if widget.include?('validate')
          validates *widget.values_at('name', 'validate')
          translate.store *widget.values_at('name', 'translate')
        end

        if widget.include?('name')
          if 'upload' == widget['type']
            has_many(:attachments)
            accepts_nested_attributes_for(:attachments)
          elsif 'repeat' == widget['type']
            part_klass = Form.compose(widget['name'], id, widget['parts'])
            embeds_many(widget['name'].pluralize, :class_name => part_klass.class.to_s)
            accepts_nested_attributes_for(widget['name'].pluralize)
          end
        end
      end

      mongoid_translate[:attributes][self.name.downcase.to_sym] = translate
    end

    I18n.backend.store_translations(:pt_BR, {:mongoid => mongoid_translate})

    form.new.tap do |form|
      form.source = source
    end
  end

  def prepare
    self.source.flatten.each do |widget|
      if widget.include?('name')
        if 'repeat' == widget['type']
          parts = send("#{widget['name'].pluralize}")

          if parts.empty?
            parts.build

            widget['parts'].each do |part|
              parts[0].write_attribute(part['name'], nil)
            end
          end
        elsif 'upload' == widget['type']
          attachments.build if attachments.empty?
        else
          begin
            send(widget['name'].to_sym)
          rescue NoMethodError
            write_attribute(widget['name'], nil)
          end
        end
      end
    end
  end
end