panel/app/helpers/application_helper.rb

module ApplicationHelper
  # Devuelve el atributo name de un campo posiblemente anidado
  def field_name_for_post(names)
    return ['post', names] if names.is_a? String

    names = names.dup
    root = 'post'
    name = names.pop
    names.each do |n|
      root = "#{root}[#{n}]"
    end

    [root, name]
  end

  def field_name_for_post_as_string(names)
    f = field_name_for_post(names)

    "#{f.first}[#{f.last}]"
  end
end