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Rails gem for dynamically adding and removing nested has_many association fields in a form. Uses jQuery and supports multiple nesting levels. Requires Ruby 1.9+ and the asset pipeline.



>= 3.2.1
>= 3.2.0
 Project Readme

Nested Form Fields Build Status

This Rails gem helps creating forms for models with nested has_many associations.

It uses jQuery to dynamically add and remove nested associations.

  • Works for arbitrarily deeply nested associations (tested up to 4 levels).
  • Works with form builders like simple_form.
  • Requires Ruby 1.9+ and the Rails asset pipeline.


Add this line to your application's Gemfile:

gem 'nested_form_fields'

And then execute:

$ bundle

In your application.js file add:

//= require nested_form_fields

Rails 5.1+

You will need to install jQuery as Rails dropped it from its default stack.

Add to Gemfile:

gem 'jquery-rails'


$ bundle

Add to application.js:

//= require jquery3
//= require jquery_ujs


Assume you have a user model with nested videos:

class User < ActiveRecord::Base
  has_many :videos
  accepts_nested_attributes_for :videos, allow_destroy: true

Use the nested_fields_for helper inside your user form to add the video fields:

= form_for @user do |f|
  = f.nested_fields_for :videos do |ff|
    = ff.text_field :video_title

Links to add and remove fields can be added using the add_nested_fields_link and remove_nested_fields_link helpers:

= form_for @user do |f|
  = f.nested_fields_for :videos do |ff|
    = ff.remove_nested_fields_link
    = ff.text_field :video_title
  = f.add_nested_fields_link :videos

Note that remove_nested_fields_link needs to be called within the nested_fields_for call and add_nested_fields_link outside of it via the parent builder.

Link Customization

You can change the link text of remove_nested_fields_link and add_nested_fields_link like this:

  ff.remove_nested_fields_link 'Remove me'
f.add_nested_fields_link :videos, 'Add another funtastic video'

You can add classes/attributes to the remove_nested_fields_link and add_nested_fields_link like this:

  ff.remove_nested_fields_link 'Remove me', class: 'btn btn-danger', role: 'button'
f.add_nested_fields_link :videos, 'Add another funtastic video', class: 'btn btn-primary', role: 'button'

You can supply a block to the remove_nested_fields_link and the add_nested_fields_link helpers, as you can with link_to:

= ff.remove_nested_fields_link do
  Remove me %span.icon-trash

You can add a data-confirm attribute to the remove_nested_fields_link if you want the user to confirm whenever they remove a nested field:

= ff.remove_nested_fields_link 'Remove me', data: { confirm: 'Are you sure?' }

Custom Container

You can specify a custom container to add nested forms into, by supplying an id via the data-insert-into attribute of the add_nested_fields_link:

f.add_nested_fields_link :videos, 'Add another funtastic video', data: { insert_into: '<container_id>' }

Custom Fields Wrapper

You can change the type of the element wrapping the nested fields using the wrapper_tag option:

= f.nested_fields_for :videos, wrapper_tag: :div do |ff|

The default wrapper element is a fieldset. To add legend element to the fieldset use:

= f.nested_fields_for :videos, legend: "Video" do |ff|

You can pass options like you would to the content_tag method by nesting them in a :wrapper_options hash:

= f.nested_fields_for :videos, wrapper_options: { class: 'row' } do |ff|

Rails 4 Parameter Whitelisting

If you are using Rails 4 remember to add {{ NESTED_MODEL }}_attributes and the attributes to the permitted params. If you want to destroy the nested model you should add :_destroy and :id. For example:

# app/views/users/_form.haml.erb
= form_for @user do |f|
  = f.nested_fields_for :videos do |ff|
    = ff.remove_nested_fields_link
    = ff.text_field :video_title
  = f.add_nested_fields_link :videos
# app/controllers/users_controller
def user_params
#                            ^^^                 ^^^           ^^^
#                            nested model attrs
#                                                             they will let you delete the nested model


There are four JavaScript events firing before and after addition/removal of the fields in the nested_form_fields namespace:

  • fields_adding
  • fields_added
  • fields_removing
  • fields_removed

The events fields_added and fields_removed are triggered on the element being added or removed. The events bubble up so you can listen for them on any parent element. This makes it easy to add listeners when you have multiple nested_form_fields on the same page.

CoffeeScript samples:

# Listen on an element
initializeSortable -> ($el)
  $el.on 'fields_added.nested_form_fields', (event, param) ->
    console.log event.target # The added field
    console.log $(this)      # $el

# Listen on document
$(document).on "fields_added.nested_form_fields", (event, param) ->
  switch param.object_class
    when "video"
      console.log "Video object added"
      console.log "INFO: Fields were successfully added, callback not handled."

You can pass any additional data to the event's callback. This may be useful if you trigger them programmatically. Example:

# Trigger button click programmatically and pass an object `{hello: 'world'}`
$('.add_nested_fields_link').trigger('click', [{hello: 'world'}])

# Listen for the event
$(document).on "fields_added.nested_form_fields", (event, param) ->
  console.log param.additional_data #=> {hello: 'world'}

Index replacement string

Sometimes your code needs to know what index it has when it is instantiated onto the page. HTML data elements may need to point to other form elements for instance. This is needed for integration with rails3-jquery-autocomplete.

To enable string substitution with the current index use the magic string __nested_field_for_replace_with_index__.


  1. Fork it
  2. Create your feature branch (git checkout -b my-new-feature)
  3. Commit your changes (git commit -am 'Added some feature')
  4. Push to the branch (git push origin my-new-feature)
  5. Create new Pull Request