Created: 2008-04-07 11:18
Updated: 2019-02-27 14:33
License: mit


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Formtastic is a Rails FormBuilder DSL (with some other goodies) to make it far easier to create beautiful, semantically rich, syntactically awesome, readily stylable and wonderfully accessible HTML forms in your Rails applications.

Documentation & Support


  • Formtastic 4 will require Rails 4.1 and Ruby 2.0 minimum
  • Formtastic 3 requires Rails 3.2.13 minimum
  • Formtastic 2 requires Rails 3
  • Formtastic, much like Rails, is very ActiveRecord-centric. Many are successfully using other ActiveModel-like ORMs and objects (DataMapper, MongoMapper, Mongoid, Authlogic, Devise...) but we're not guaranteeing full compatibility at this stage. Patches are welcome!

The Story

One day, I finally had enough, so I opened up my text editor, and wrote a DSL for how I'd like to author forms:

  <%= semantic_form_for @article do |f| %>

    <%= f.inputs :name => "Basic" do %>
      <%= f.input :title %>
      <%= f.input :body %>
      <%= f.input :section %>
      <%= f.input :publication_state, :as => :radio %>
      <%= f.input :category %>
      <%= f.input :allow_comments, :label => "Allow commenting on this article" %>
    <% end %>

    <%= f.inputs :name => "Advanced" do %>
      <%= f.input :keywords, :required => false, :hint => "Example: ruby, rails, forms" %>
      <%= f.input :extract, :required => false %>
      <%= f.input :description, :required => false %>
      <%= f.input :url_title, :required => false %>
    <% end %>

    <%= f.inputs :name => "Author", :for => :author do |author_form| %>
      <%= author_form.input :first_name %>
      <%= author_form.input :last_name %>
    <% end %>

    <%= f.actions do %>
      <%= f.action :submit, :as => :button %>
      <%= f.action :cancel, :as => :link %>
    <% end %>

  <% end %>

I also wrote the accompanying HTML output I expected, favoring something very similar to the fieldsets, lists and other semantic elements Aaron Gustafson presented in Learning to Love Forms, hacking together enough Ruby to prove it could be done.

It's awesome because...

  • It can handle belongs_to associations (like Post belongs_to :author), rendering a select or set of radio inputs with choices from the parent model.
  • It can handle has_many and has_and_belongs_to_many associations (like: Post has_many :tags), rendering a multi-select with choices from the child models.
  • It's Rails 3/4 compatible (including nested forms).
  • It has internationalization (I18n)!
  • It's really quick to get started with a basic form in place (4 lines), then go back to add in more detail if you need it.
  • There's heaps of elements, id and class attributes for you to hook in your CSS and JS.
  • It handles real world stuff like inline hints, inline error messages & help text.
  • It doesn't hijack or change any of the standard Rails form inputs, so you can still use them as expected (even mix and match).
  • It's got absolutely awesome spec coverage.
  • There's a bunch of people using and working on it (it's not just one developer building half a solution).
  • It has growing HTML5 support (new inputs like email/phone/search, new attributes like required/min/max/step/placeholder)


  • It should be easier to do things the right way than the wrong way.
  • Sometimes more mark-up is better.
  • Elements and attribute hooks are gold for stylesheet authors.
  • Make the common things we do easy, yet ensure uncommon things are still possible.


Simply add Formtastic to your Gemfile and bundle it up:

  gem 'formtastic', '~> 3.0'

Run the installation generator:

$ rails generate formtastic:install


A proof-of-concept set of stylesheets are provided which you can include in your layout. Customization is best achieved by overriding these styles in an additional stylesheet.

Rails 3.1 introduces an asset pipeline that allows plugins like Formtastic to serve their own Stylesheets, Javascripts, etc without having to run generators that copy them across to the host application. Formtastic makes three stylesheets available as an Engine, you just need to require them in your global stylesheets.

  # app/assets/stylesheets/application.css
  *= require formtastic
  *= require my_formtastic_changes

Conditional stylesheets need to be compiled separately to prevent them being bundled and included with other application styles. Remove require_tree . from application.css and specify required stylesheets individually.

  # app/assets/stylesheets/ie6.css
  *= require formtastic_ie6

  # app/assets/stylesheets/ie7.css
  *= require formtastic_ie7
  # app/views/layouts/application.html.erb
  <%= stylesheet_link_tag 'application' %>
  <!--[if IE 6]><%= stylesheet_link_tag 'ie6' %><![endif]-->
  <!--[if IE 7]><%= stylesheet_link_tag 'ie7' %><![endif]-->
  # config/environments/production.rb
  config.assets.precompile += %w( ie6.css ie7.css )


Forms are really boring to code... you want to get onto the good stuff as fast as possible.

This renders a set of inputs (one for most columns in the database table, and one for each ActiveRecord belongs_to-association), followed by default action buttons (an input submit button):

  <%= semantic_form_for @user do |f| %>
    <%= f.inputs %>
    <%= f.actions %>
  <% end %>

This is a great way to get something up fast, but like scaffolding, it's not recommended for production. Don't be so lazy!

To specify the order of the fields, skip some of the fields or even add in fields that Formtastic couldn't infer. You can pass in a list of field names to inputs and list of action names to actions:

  <%= semantic_form_for @user do |f| %>
    <%= f.inputs :title, :body, :section, :categories, :created_at %>
    <%= f.actions :submit, :cancel %>
  <% end %>

You probably want control over the input type Formtastic uses for each field. You can expand the inputs and actions to block helper format and use the :as option to specify an exact input type:

  <%= semantic_form_for @post do |f| %>
    <%= f.inputs do %>
      <%= f.input :title %>
      <%= f.input :body %>
      <%= f.input :section, :as => :radio %>
      <%= f.input :categories %>
      <%= f.input :created_at, :as => :string %>
    <% end %>
    <%= f.actions do %>
      <%= f.action :submit, :as => :button %>
      <%= f.action :cancel, :as => :link %>
    <% end %>
  <% end %>

If you want to customize the label text, or render some hint text below the field, specify which fields are required/optional, or break the form into two fieldsets, the DSL is pretty comprehensive:

  <%= semantic_form_for @post do |f| %>
    <%= f.inputs "Basic", :id => "basic" do %>
      <%= f.input :title %>
      <%= f.input :body %>
    <% end %>
    <%= f.inputs :name => "Advanced Options", :id => "advanced" do %>
      <%= f.input :slug, :label => "URL Title", :hint => "Created automatically if left blank", :required => false %>
      <%= f.input :section, :as => :radio %>
      <%= f.input :user, :label => "Author" %>
      <%= f.input :categories, :required => false %>
      <%= f.input :created_at, :as => :string, :label => "Publication Date", :required => false %>
    <% end %>
    <%= f.actions do %>
      <%= f.action :submit %>
    <% end %>
  <% end %>

You can create forms for nested resources:

	<%= semantic_form_for [@author, @post] do |f| %>

Nested forms are also supported (don't forget your models need to be setup correctly with accepts_nested_attributes_for). You can do it in the Rails way:

  <%= semantic_form_for @post do |f| %>
    <%= f.inputs :title, :body, :created_at %>
    <%= f.semantic_fields_for :author do |author| %>
      <%= author.inputs :first_name, :last_name, :name => "Author" %>
    <% end %>
    <%= f.actions %>
  <% end %>

Or the Formtastic way with the :for option:

  <%= semantic_form_for @post do |f| %>
    <%= f.inputs :title, :body, :created_at %>
    <%= f.inputs :first_name, :last_name, :for => :author, :name => "Author" %>
    <%= f.actions %>
  <% end %>

When working in has many association, you can even supply "%i" in your fieldset name; they will be properly interpolated with the child index. For example:

  <%= semantic_form_for @post do |f| %>
    <%= f.inputs %>
    <%= f.inputs :name => 'Category #%i', :for => :categories %>
    <%= f.actions %>
  <% end %>

Alternatively, the current index can be accessed via the inputs block's arguments for use anywhere:

  <%= semantic_form_for @post do |f| %>
    <%= f.inputs :for => :categories do |category, i| %>
    <%= f.actions %>
  <% end %>

If you have more than one form on the same page, it may lead to HTML invalidation because of the way HTML element id attributes are assigned. You can provide a namespace for your form to ensure uniqueness of id attributes on form elements. The namespace attribute will be prefixed with underscore on the generate HTML id. For example:

  <%= semantic_form_for(@post, :namespace => 'cat_form') do |f| %>
    <%= f.inputs do %>
      <%= f.input :title %>        # id="cat_form_post_title"
      <%= f.input :body %>         # id="cat_form_post_body"
      <%= f.input :created_at %>   # id="cat_form_post_created_at"
    <% end %>
    <%= f.actions %>
  <% end %>

Customize HTML attributes for any input using the :input_html option. Typically this is used to disable the input, change the size of a text field, change the rows in a textarea, or even to add a special class to an input to attach special behavior like autogrow textareas:

  <%= semantic_form_for @post do |f| %>
    <%= f.inputs do %>
      <%= f.input :title,      :input_html => { :size => 10 } %>
      <%= f.input :body,       :input_html => { :class => 'autogrow', :rows => 10, :cols => 20, :maxlength => 10  } %>
      <%= f.input :created_at, :input_html => { :disabled => true } %>
      <%= f.input :updated_at, :input_html => { :readonly => true } %>
    <% end %>
    <%= f.actions %>
  <% end %>

The same can be done for actions with the :button_html option:

  <%= semantic_form_for @post do |f| %>
    <%= f.actions do %>
      <%= f.action :submit, :button_html => { :class => "primary", :disable_with => 'Wait...' } %>
    <% end %>
  <% end %>

Customize the HTML attributes for the <li> wrapper around every input with the :wrapper_html option hash. There's one special key in the hash: (:class), which will actually append your string of classes to the existing classes provided by Formtastic (like "required string error").

  <%= semantic_form_for @post do |f| %>
    <%= f.inputs do %>
      <%= f.input :title, :wrapper_html => { :class => "important" } %>
      <%= f.input :body %>
      <%= f.input :description, :wrapper_html => { :style => "display:none;" } %>
    <% end %>
  <% end %>

Many inputs provide a collection of options to choose from (like :select, :radio, :check_boxes, :boolean). In many cases, Formtastic can find choices through the model associations, but if you want to use your own set of choices, the :collection option is what you want. You can pass in an Array of objects, an array of Strings, a Hash... Throw almost anything at it! Examples:

  f.input :authors, :as => :check_boxes, :collection => User.order("last_name ASC").all
  f.input :authors, :as => :check_boxes, :collection =>
  f.input :authors, :as => :check_boxes, :collection => [@justin, @kate]
  f.input :authors, :as => :check_boxes, :collection => ["Justin", "Kate", "Amelia", "Gus", "Meg"]
  f.input :author,  :as => :select,      :collection => Author.all
  f.input :author,  :as => :select,      :collection => Author.pluck(:first_name, :id)
  f.input :author,  :as => :select,      :collection => Author.pluck(Arel.sql("CONCAT(`first_name`, ' ', `last_name`)"), :id)
  f.input :author,  :as => :select,      :collection => Author.your_custom_scope_or_class_method
  f.input :author,  :as => :select,      :collection => { =>, => }
  f.input :author,  :as => :select,      :collection => ["Justin", "Kate", "Amelia", "Gus", "Meg"]
  f.input :author,  :as => :radio,       :collection => User.all
  f.input :author,  :as => :radio,       :collection => [@justin, @kate]
  f.input :author,  :as => :radio,       :collection => { =>, => }
  f.input :author,  :as => :radio,       :collection => ["Justin", "Kate", "Amelia", "Gus", "Meg"]
  f.input :admin,   :as => :radio,       :collection => ["Yes!", "No"]
  f.input :book_id, :as => :select,      :collection => Hash[{|b| [,]}]
  f.input :fav_book,:as => :datalist   , :collection => Book.pluck(:name)

The Available Inputs

The Formtastic input types:

  • :select - a select menu. Default for ActiveRecord associations: belongs_to, has_many, and has_and_belongs_to_many.
  • :check_boxes - a set of check_box inputs. Alternative to :select for ActiveRecord-associations: has_many, and has_and_belongs_to_many`.
  • :radio - a set of radio inputs. Alternative to :select for ActiveRecord-associations: belongs_to.
  • :time_zone - a select input. Default for column types: :string with name matching "time_zone".
  • :password - a password input. Default for column types: :string with name matching "password".
  • :text - a textarea. Default for column types: :text.
  • :date_select - a date select. Default for column types: :date.
  • :datetime_select - a date and time select. Default for column types: :datetime and :timestamp.
  • :time_select - a time select. Default for column types: :time.
  • :boolean - a checkbox. Default for column types: :boolean.
  • :string - a text field. Default for column types: :string.
  • :number - a text field (just like string). Default for column types: :integer, :float, and :decimal.
  • :file - a file field. Default for file-attachment attributes matching: paperclip or attachment_fu.
  • :country - a select menu of country names. Default for column types: :string with name "country" - requires a country_select plugin to be installed.
  • :email - a text field (just like string). Default for columns with name matching "email". New in HTML5. Works on some mobile browsers already.
  • :url - a text field (just like string). Default for columns with name matching "url". New in HTML5. Works on some mobile browsers already.
  • :phone - a text field (just like string). Default for columns with name matching "phone" or "fax". New in HTML5.
  • :search - a text field (just like string). Default for columns with name matching "search". New in HTML5. Works on Safari.
  • :hidden - a hidden field. Creates a hidden field (added for compatibility).
  • :range - a slider field.
  • :datalist - a text field with a accompanying datalist tag which provides options for autocompletion

The comments in the code are pretty good for each of these (what it does, what the output is, what the options are, etc.) so go check it out.

Delegation for label lookups

Formtastic decides which label to use in the following order:

  1. :label             # :label => "Choose Title"
  2. Formtastic i18n    # if either :label => true || i18n_lookups_by_default = true (see Internationalization)
  3. Activerecord i18n  # if localization file found for the given attribute
  4. label_str_method   # if nothing provided this defaults to :humanize but can be set to a custom method

Internationalization (I18n)

Basic Localization

Formtastic has some neat I18n-features. ActiveRecord object names and attributes are, by default, taken from calling @object.human_name and @object.human_attribute_name(attr) respectively. There are a few words specific to Formtastic that can be translated. See lib/locale/en.yml for more information.

Basic localization (labels only, with ActiveRecord):

  <%= semantic_form_for @post do |f| %>
    <%= f.inputs do %>
      <%= f.input :title %>        # => :label => I18n.t('activerecord.attributes.user.title')    or 'Title'
      <%= f.input :body %>         # => :label => I18n.t('activerecord.attributes.user.body')     or 'Body'
      <%= f.input :section %>      # => :label => I18n.t('activerecord.attributes.user.section')  or 'Section'
    <% end %>
  <% end %>

Note: This is perfectly fine if you just want your labels/attributes and/or models to be translated using ActiveRecord I18n attribute translations, and you don't use input hints and legends. But what if you do? And what if you don't want same labels in all forms?

Enhanced Localization (Formtastic I18n API)

Formtastic supports localized labels, hints, legends, actions using the I18n API for more advanced usage. Your forms can now be DRYer and more flexible than ever, and still fully localized. This is how:

1. Enable I18n lookups by default (config/initializers/formtastic.rb):

  Formtastic::FormBuilder.i18n_lookups_by_default = true

2. Add some label-translations/variants (config/locales/en.yml):

        post_details: "Post details"
          title: "Your Title"
          body: "Write something..."
            title: "Edit title"
          title: "Choose a good title for your post."
          body: "Write something inspiring here."
          title: "Title your post"
          slug: "Leave blank for an automatically generated slug"
          email: ""
        create: "Create my %{model}"
        update: "Save changes"
        reset: "Reset form"
        cancel: "Cancel and go back"
        dummie: "Launch!"

3. ...and now you'll get:

  <%= semantic_form_for do |f| %>
    <%= f.inputs do %>
      <%= f.input :title %>      # => :label => "Choose a title...", :hint => "Choose a good title for your post."
      <%= f.input :body %>       # => :label => "Write something...", :hint => "Write something inspiring here."
      <%= f.input :section %>    # => :label => I18n.t('activerecord.attributes.user.section')  or 'Section'
    <% end %>
    <%= f.actions do %>
      <%= f.action :submit %>   # => "Create my %{model}"
    <% end %>
  <% end %>

4. Localized titles (a.k.a. legends):

Note: Slightly different because Formtastic can't guess how you group fields in a form. Legend text can be set with first (as in the sample below) specified value, or :name/:title options - depending on what flavor is preferred.

  <%= semantic_form_for