Gem provide API (scripts, helpers, controller and base class for ajax-search) for initialize different select2 elements: static, ajax and multi-ajax.

The AutoSelect2 based on select2-rails gem.

Gem Version



Install select2-rails and include javascript and stylesheet assets as described on select2-rails page.


Add this line to your application's Gemfile:

gem 'auto_select2'

And then execute:

$ bundle


Select one of ways to include js in pipeline. Ways described below in section Javascript include variants


Check controller and route collation. Gem contain controller Select2AutocompletesController and route

get 'select2_autocompletes/:class_name'


Prepare folder app/select2_search_adapter if you want to use ajax-select2. This folder needed for storage custom SearchAdapter.


Gem tested and works in Rails 3.2 and Rails 4.0. You can test compatibility with other versions by yourself.

Easiest way to use

Use AutoSelect2Tag. It provide helpers:

  • select2_tag
  • select2_ajax_tag

and you can define select2 element like any other view elements in rails.


You can find example project here.


Element types

Gem provides 3 types of select2 elements:

  • static
  • ajax
  • multi-ajax

For each of it exist javascript initializer. This is:

  • static_select2.js
  • ajax_select2.js
  • multi_ajax_select2_value_parser.js

Note: multi_ajax_select2_value_parser.js work only together with ajax_select2.js

Javascript include variants

You have two ways to include javascript files. First: in gem presents helper methods

  • static_select2_init_header_tags
  • ajax_select2_init_header_tags
  • ajax_multi_select2_init_header_tags

These helpers call javascript_include_tag and it is useful for initialize select2 scripts on a single page. Example of usage in a view:

- static_select2_init_header_tags

  = select2_tag :my_select, my_options_for_select, class: 'small'

Second variant: include files in javascript assets. For this add the following to your app/assets/javascripts/application.js:

//= require auto_select2/static_select2
//= require auto_select2/ajax_select2
//= require auto_select2/multi_ajax_select2_value_parser

Select2 options

If you want to specify any parameters for select2 constructor you can pass it as hash into data-attribute s2-options. This parameter handle most options but you can't pass through js-functions.

Static select2 usage

For initialize static select2 you must set auto-static-select2 css-class for select element:

= select_tag :my_select, my_options_for_select, class: 'my-class auto-static-select2'

Ajax select2 usage

For initialize ajax select 2 you must set auto-ajax-select2 css-class for hidden-input element. Then you need to create a SearchAdapter. This adapter has following requirements:

  • class must be inherited from AutoSelect2::Select2SearchAdapter::Base
  • file must be put in any folder which included into autoload path, preferably in app/select2_search_adapter
  • name of a adapter class must end with SearchAdapter
  • must has function search_default(term, page, options) (description of the function and return value goes below)

Returned value of search_default function must be follow:

  • if options contain :init key function must return hash {text: 'displayed text', id: 'id_of_initial_element'}
  • otherwise function must return the follow hash:

    { items: [ { text: 'first element', id: 'first_id' }, { text: 'second element', id: 'second_id' } ], total: count }

Here in "total" must be specified amount of all select variants. For example you have select element with 42 variants. Function search_default return part of it in items and in total each time you must set 42.

TIP: in search_default you can use functions from AutoSelect2::Select2SearchAdapter::Base:

  • default_finder(searched_class, term, options)
  • default_count(searched_class, term, options = {})
  • get_init_values(searched_class, ids, title_method=nil)

More about this function you can find in example project, in example below and in source code.

Finally hidden-input must has :href parameter in data-attribute s2-options. This parameter specify url for ajax load select options. You can use path-helper select2_autocompletes_path for this purpose.

Example of minimalistic SearchAdapter

class SystemRoleSearchAdapter < AutoSelect2::Select2SearchAdapter::Default
  searchable_class SystemRole
  id_column :id
  text_columns: :name
  hash_method :to_select2 # optional

More complex example:

class SystemRoleSearchAdapter < AutoSelect2::Select2SearchAdapter::Base
  class << self
    def search_default(term, page, options)
      if options[:init].nil?
        roles = default_finder(SystemRole, term, page: page)
        count = default_count(SystemRole, term)
          items: do |role|
            { text:, id: } # here is optional parameter 'class_name'
          total: count
        get_init_values(SystemRole, options[:item_ids])


Gem provide a rails generator for creating a simple SearchAdapter like a first one from previous section. Run follows command:

rails generate auto_select2:search_adapter TargetModelName --id-column=name_of_id_column  --text-columns=name_of_columns_for_searching_by

Available options for generator:

  • id-column - name of model column with identifier;
  • text-columns - column for searching by (available multiple values, for example "--text-columns=name description" without coma);
  • hash-method - instance method of model for converting into Hash for transporting into select2 (optional);
  • destination-path - path for storing SearchAdapter classes (optional, default: 'app/select2_search_adapters').

More about SearchAdapter

SearchAdapter has some additional functions. First, you can define multiple search functions in one adapter. For example in adapter for User you want to find among all users, find users only in one department and so on. For this purpose define methods like

def search_unusual_case(term, page, options)
  # must has same behavior as search_default

near the search_default in SearchAdapter. Requirement for non-default search methods:

  • it must has same behavior as search_default
  • name of methods must start with search_

For use custom searcher specify it into :href within data-attribute s2-options:

select2_autocompletes_path(class_name: MyClassName, search_method: :unusual_case)

Second, you may want to pass additional parameters in SearchAdapter. For example select options depend from another field on page. For this purpose you can specify

additional_ajax_data: {selector: 'input.css-class'}

inside data-attribute s2-options. In this case in options of SearchAdapter appear additional values. It construct from name and value of html-elements. Example:

= hidden_field_tag 'token', '[email protected]', class: 'add-to-select2'
= hidden_field_tag 'select2element', '',
                    class: 'auto-ajax-select2',
                    data: {s2-options: { href: select2_autocompletes_path(class_name: :adapter_name,
                                                                         search_method: :unusual_case),
                                        additional_ajax_data: {selector: '.add-to-select2'}}}

Here we initialize ajax select2 and during load select variants in SearchAdapter options hash appear key :token with value '[email protected]'.

Moreover you may pass name of js function into additional_ajax_data:

additional_ajax_data: {selector: 'input.css-class',
                       function: 'additionalGlobalJsFunctionForRequestParameters'}

In this case function additionalGlobalJsFunctionForRequestParameters must looks follows:

window.additionalGlobalJsFunctionForRequestParameters = function($element, $term) {

  // any js actions

  return {
    additional_param: '42',
    awesome_option: 'something especial'

As you see, function receive two arguments: select2_element (i.e. initial input field) and term (i.e. text from input). Return value of the function must be a hash. This hash merged into ajax data and can be obtained in SearchAdapter.

Third, in hash with items from search method exist additional optional parameter class_name. This parameter specify css-class for result element in select2. It useful for show different icons for different select variants.

Multi ajax select2 usage

This feature require absolutely same things as ajax select2. Additionally you must add multiple css-class for input element, doesn't forget about multi_ajax_select2_value_parser.js script and pass multiple: true into data-attribute s2-options.

Different multi ajax select2

Honestly speaking you can just pass multiple: true into data-attribute s2-options and ajax-select2 become multiple. But in this case selected options from select2 become as comma separated string. As opposed to it multi_ajax_select2_value_parser.js make array of multiple ids. This is more comfortable for use in controller.


Scripts automatically initialize on $(document).ready() and after ajaxSuccess. Moreover script handle cocoon events and run on cocoon:after-insert. If you for any reasons want to manually initializing select2, you can call initAutoAjaxSelect2() and/or initAutoStaticSelect2().


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