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An extension of Formtastic form builder to make building nested and association form extremely simple
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An extension of famous Formtastic Form Builder to make building nested and association form with nested model addable and removable ability extremely easy and simple.

Checkout the the Demo


  • Formnestic gem requires formtastic gem version >= 2.2.1
  • Formnestic gem is Rails 3 and Rails 4 compatible


Add Formnestic to your Gemfile and run bundle install:

gem "formnestic", '~> 1.0.2'

then run the installation

bundle exec rails g formnestic:install


  • Table form with row addable and removable
  • List form with entry addable and removable


Usage for rails 3 and rails 4 are almost the same, the only difference is that in Rails 4, you will need to remove all the attr_accessible in Rails 3 and use strong parameters in rails controller.

Basically, you can now add the following options into semantic_fields_for call in Formtastic

  • display_type: If you want your nested form to have table style, you can supply in table string
  • row_removable: Allow nested model entry to be removed.
  • row_addable: Allow nested model entry to be added.
  • min_entry: Minimum number of nested model entries that is allowed. An alert will be shown if user tries to delete the last entry that meets this minumum number.
  • max_entry: Maximum number of nested model entries that is allowed. Add button will be hidden if user has already added enough entries.
  • new_record_link_label: The label to be displayed in the Add button.
  • table_headers: A two(2) dimensional arrays, in which each array is presenting a row in table header row. For instance:
  [{label: 'Column 1', wrapper_html: {class: "big-column"}}, {label: 'Column 2'}],
  [{attr: :name}, {attr: :description}],

will yield a table header with 2 rows. The first row has 2 columns labeled Column 1 and Column 2 respectively, the second row labelled respected attribute's name of the nested model.

The form view is the same between Rails 3 and Rails 4

<%= semantic_form_for @quiz_pool do |quiz_pool_form| %>
  <%= quiz_pool_form.inputs do %>
    <%= quiz_pool_form.input :title %>
    <%= quiz_pool_form.input :description %>
      <%= quiz_pool_form.semantic_fields_for :quiz_pool_questions, {
        row_removable: true, 
        row_addable: true,
        min_entry: 1, 
        max_entry: 5,
        new_record_link_label: "+ question"
      } do |quiz_pool_question_builder| %>
        <%= quiz_pool_question_builder.inputs do %>
          <%= quiz_pool_question_builder.input :description %>
          <%= quiz_pool_question_builder.input :score %>
        <% end %>
      <% end %>
  <% end %>
  <%= quiz_pool_form.submit %>
<% end %>

See the usage for each of Rails version below for more details

Rails 3 Usage

Rails 4 Usage


Table Form

Table Form

List Form

List Form

Roadmap to version 2.0

  • Sortable between nested model entry (including rows in a table)
  • Delegator for alert view
  • Ability to lock an entry

Contributing to formnestic

  • Contribution, Suggestion and Issues are very much appreciated :). Please also fork and send your pull request!
  • Make sure to add tests for it when sending for pull requests. This is important so I don't break it in a future version unintentionally.


  • Big thanks to Justin French for bringing Formtastic to our lives. It has enabled us to effectively code form much easier in rails and has enabled this gem to happen.


Copyright (c) 2014 James, released under the MIT license

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