Gild

class LinkBuilder < Gild::Builder
  helper  Rails.application.routes.url_helpers
  helper SomeOtherHelper

  template do
    object @link, :attributes => [:id, :url, :status] do
      attribute(:created_at) { |created_at| created_at.to_s(:custom_format) }

      object :resources do
        virtual(:show_path) { |link| link_path(link) }
      end

      object @link.submitter, :as => :submitted_by do
        attributes [:sidereel_id, :sidereel_type]
      end
    end
  end

  array @alternate_links, :attributes => [:id, :url, :status]
end

LinkBuilder.render("@link" => link, "@alternate_links" =>
alternate_links).to_hash

Which would yield:

{
  link => {
    'id' => 1,
    'url' => "http://www.example.com/1",
    'status' => "processed",
    'created_at' => "November 5, 2011",

    'resources' => { 'show_path' => 'links/1' },
    'submitted_by' => { 'sidereel_id' => 1, 'sidereel_type' => "Admin" }
  }

  links => [
    { "id" => 2, "url" => "http://www.example.com/2", "status" =>
processed" },
    { "id" => 3, "url" => "http://www.example.com/3", "status" =>
processed" },
    { "id" => 4, "url" => "http://www.example.com/4", "status" =>
processed" }
  ]
}

The DSL also supports rendering other Builders (essentiall you'd call 'render SomeOtherBuilder'). The render call can be called from anywhere. It just starts dumping its output at the level you called it at.

Its three small classes. Next up would be rails support and some configuration (like don't render null values).