engine/app/helpers/locomotive/content_entries_helper.rb

module Locomotive::ContentEntriesHelper

  def options_for_belongs_to_custom_field(class_name)
    content_type = Locomotive::ContentType.class_name_to_content_type(class_name, current_site)

    if content_type
      content_type.ordered_entries.map { |entry| [entry._label, entry._id] }
    else
      [] # unknown content type
    end
  end

end