This is an example of a field set using the nested_form gem along with the twitter bootstrap style framework. It enables very efficient editing of data and relationships since three objects can be edited at once. Instead of being directed to another form and having to go back, ajax is used to create a dynamic form.

double_nested_fields.html.haml

%li.reference_group
  .container-fluid
    .row-fluid
      .span1.move
        %i.icon-move
      .span4
        = f.input_field :label_markdown, placeholder: '<markdown enabled>'
        = f.input :order, as: :hidden
      .span7
        = f.link_to_remove class: 'btn btn-danger' do
          %i.icon-minus-sign.icon-white
    .row-fluid.references_container
      .span12
        = f.link_to_add :references, class: 'btn' do
          %i.icon-plus
          Add Reference
        %ul.sortable.references
          = f.fields_for :references do |ff|
            %li.reference
              .row-fluid
                .span1.move
                  %i.icon-move
                .span11
                  = render "admin/reference_fields", f: ff