Simple Form

Bootstrap 5

Simple Form can be easily integrated with Bootstrap 5. Use the bootstrap option in the install generator, like this:

rails generate simple_form:install --bootstrap

This will add an initializer that configures Simple Form wrappers for Bootstrap 5’s form controls. You have to be sure that you added a copy of the Bootstrap assets on your application.

For more information see the generator output, our example application code and the live example app.

Country Select

If you want to use the country select, you will need the country_select gem, add it to your Gemfile:

gem 'country_select'

If you don’t want to use the gem you can easily override this behaviour by mapping the country inputs to something else, with a line like this in your simple_form.rb initializer:

config.input_mappings = { /country/ => :string }

Stripping away all wrapper divs

Simple Form also allows you to strip away all the div wrappers around the <input> field that is generated with the usual f.input. The easiest way to achieve this is to use f.input_field.

Example:

simple_form_for @user do |f|
  f.input_field :name
  f.input_field :remember_me, as: :boolean
end

<form>
  ...
  <input class="string required" id="user_name" maxlength="255" name="user[name]" size="255" type="text">
  <input name="user[remember_me]" type="hidden" value="0">
  <label class="checkbox">
    <input class="boolean optional" id="user_published" name="user[remember_me]" type="checkbox" value="1">
  </label>
</form>

For check boxes and radio buttons you can remove the label changing boolean_style from default value :nested to :inline.

Example:

simple_form_for @user do |f|
  f.input_field :name
  f.input_field :remember_me, as: :boolean, boolean_style: :inline
end

<form>
  ...
  <input class="string required" id="user_name" maxlength="255" name="user[name]" size="255" type="text">
  <input name="user[remember_me]" type="hidden" value="0">
  <input class="boolean optional" id="user_remember_me" name="user[remember_me]" type="checkbox" value="1">
</form>

To view the actual RDocs for this, check them out here - http://rubydoc.info/github/heartcombo/simple_form/main/SimpleForm/FormBuilder:input_field

Collections

And what if you want to create a select containing the age from 18 to 60 in your form? You can do it overriding the :collection option:

<%= simple_form_for @user do |f| %>
  <%= f.input :user %>
  <%= f.input :age, collection: 18..60 %>
  <%= f.button :submit %>
<% end %>

Collections can be arrays or ranges, and when a :collection is given the :select input will be rendered by default, so we don’t need to pass the as: :select option. Other types of collection are :radio_buttons and :check_boxes. Those are added by Simple Form to Rails set of form helpers (read Extra Helpers section below for more information).

Collection inputs accept two other options beside collections:

label_method => the label method to be applied to the collection to retrieve the label (use this instead of the text_method option in collection_select)
value_method => the value method to be applied to the collection to retrieve the value

Those methods are useful to manipulate the given collection. Both of these options also accept lambda/procs in case you want to calculate the value or label in a special way eg. custom translation. You can also define a to_label method on your model as Simple Form will search for and use :to_label as a :label_method first if it is found.

By default, Simple Form will use the first item from an array as the label and the second one as the value. If you want to change this behavior you must make it explicit, like this:

<%= simple_form_for @user do |f| %>
  <%= f.input :gender, as: :radio_buttons, collection: [['0', 'female'], ['1', 'male']], label_method: :second, value_method: :first %>
<% end %>

All other options given are sent straight to the underlying Rails helper(s): collection_select, collection_check_boxes, collection_radio_buttons. For example, you can pass prompt and selected as:

f.input :age, collection: 18..60, prompt: "Select your age", selected: 21

It may also be useful to explicitly pass a value to the optional :selected like above, especially if passing a collection of nested objects.

It is also possible to create grouped collection selects, that will use the html optgroup tags, like this:

f.input :country_id, collection: @continents, as: :grouped_select, group_method: :countries

Grouped collection inputs accept the same :label_method and :value_method options, which will be used to retrieve label/value attributes for the option tags. Besides that, you can give:

group_method => the method to be called on the given collection to generate the options for each group (required)
group_label_method => the label method to be applied on the given collection to retrieve the label for the optgroup (Simple Form will attempt to guess the best one the same way it does with :label_method)

Associations

To deal with associations, Simple Form can generate select inputs, a series of radios buttons or checkboxes. Lets see how it works: imagine you have a user model that belongs to a company and has_and_belongs_to_many roles. The structure would be something like:

class User < ActiveRecord::Base
  belongs_to :company
  has_and_belongs_to_many :roles
end

class Company < ActiveRecord::Base
  has_many :users
end

class Role < ActiveRecord::Base
  has_and_belongs_to_many :users
end

Now we have the user form:

<%= simple_form_for @user do |f| %>
  <%= f.input :name %>
  <%= f.association :company %>
  <%= f.association :roles %>
  <%= f.button :submit %>
<% end %>

Simple enough, right? This is going to render a :select input for choosing the :company, and another :select input with :multiple option for the :roles. You can, of course, change it to use radio buttons and checkboxes as well:

f.association :company, as: :radio_buttons
f.association :roles,   as: :check_boxes

The association helper just invokes input under the hood, so all options available to :select, :radio_buttons and :check_boxes are also available to association. Additionally, you can specify the collection by hand, all together with the prompt:

f.association :company, collection: Company.active.order(:name), prompt: "Choose a Company"

In case you want to declare different labels and values:

f.association :company, label_method: :company_name, value_method: :id, include_blank: false

Please note that the association helper is currently only tested with Active Record. It currently does not work well with Mongoid and depending on the ORM you’re using your mileage may vary.

Buttons

All web forms need buttons, right? Simple Form wraps them in the DSL, acting like a proxy:

<%= simple_form_for @user do |f| %>
  <%= f.input :name %>
  <%= f.button :submit %>
<% end %>

The above will simply call submit. You choose to use it or not, it’s just a question of taste.

The button method also accepts optional parameters, that are delegated to the underlying submit call:

<%= f.button :submit, "Custom Button Text", class: "my-button" %>

To create a <button> element, use the following syntax:

<%= f.button :button, "Custom Button Text" %>

<%= f.button :button do %>
  Custom Button Text
<% end %>

Wrapping Rails Form Helpers

Say you wanted to use a rails form helper but still wrap it in Simple Form goodness? You can, by calling input with a block like so:

<%= f.input :role do %>
  <%= f.select :role, Role.all.map { |r| [r.name, r.id, { class: r.company.id }] }, include_blank: true %>
<% end %>

In the above example, we’re taking advantage of Rails 3’s select method that allows us to pass in a hash of additional attributes for each option.

Extra helpers

Simple Form also comes with some extra helpers you can use inside rails default forms without relying on simple_form_for helper. They are listed below.

Simple Fields For

Wrapper to use Simple Form inside a default rails form. It works in the same way that the fields_for Rails helper, but change the builder to use the SimpleForm::FormBuilder.

form_for @user do |f|
  f.simple_fields_for :posts do |posts_form|
    # Here you have all simple_form methods available
    posts_form.input :title
  end
end

Collection Radio Buttons

Creates a collection of radio inputs with labels associated (same API as collection_select):

form_for @user do |f|
  f.collection_radio_buttons :options, [[true, 'Yes'], [false, 'No']], :first, :last
end

<input id="user_options_true" name="user[options]" type="radio" value="true" />
<label class="collection_radio_buttons" for="user_options_true">Yes</label>
<input id="user_options_false" name="user[options]" type="radio" value="false" />
<label class="collection_radio_buttons" for="user_options_false">No</label>

Collection Check Boxes

Creates a collection of checkboxes with labels associated (same API as collection_select):

form_for @user do |f|
  f.collection_check_boxes :options, [[true, 'Yes'], [false, 'No']], :first, :last
end

<input name="user[options][]" type="hidden" value="" />
<input id="user_options_true" name="user[options][]" type="checkbox" value="true" />
<label class="collection_check_box" for="user_options_true">Yes</label>
<input name="user[options][]" type="hidden" value="" />
<input id="user_options_false" name="user[options][]" type="checkbox" value="false" />
<label class="collection_check_box" for="user_options_false">No</label>

To use this with associations in your model, you can do the following:

form_for @user do |f|
  f.collection_check_boxes :role_ids, Role.all, :id, :name # using :roles here is not going to work.
end

To add a CSS class to the label item, you can use the item_label_class option:

f.collection_check_boxes :role_ids, Role.all, :id, :name, item_label_class: 'my-custom-class'

Available input types and defaults for each column type

The following table shows the html element you will get for each attribute according to its database definition. These defaults can be changed by specifying the helper method in the column Mapping as the as: option.

Mapping	Generated HTML Element	Database Column Type
`boolean`	`input[type=checkbox]`	`boolean`
`string`	`input[type=text]`	`string`
`citext`	`input[type=text]`	`citext`
`email`	`input[type=email]`	`string` with `name =~ /email/`
`url`	`input[type=url]`	`string` with `name =~ /url/`
`tel`	`input[type=tel]`	`string` with `name =~ /phone/`
`password`	`input[type=password]`	`string` with `name =~ /password/`
`search`	`input[type=search]`	-
`uuid`	`input[type=text]`	`uuid`
`color`	`input[type=color]`	`string`
`text`	`textarea`	`text`
`hstore`	`textarea`	`hstore`
`json`	`textarea`	`json`
`jsonb`	`textarea`	`jsonb`
`file`	`input[type=file]`	`string` responding to file methods
`hidden`	`input[type=hidden]`	-
`integer`	`input[type=number]`	`integer`
`float`	`input[type=number]`	`float`
`decimal`	`input[type=number]`	`decimal`
`range`	`input[type=range]`	-
`datetime`	`datetime select`	`datetime/timestamp`
`date`	`date select`	`date`
`time`	`time select`	`time`
`select`	`select`	`belongs_to`/`has_many`/`has_and_belongs_to_many` associations
`radio_buttons`	collection of `input[type=radio]`	`belongs_to` associations
`check_boxes`	collection of `input[type=checkbox]`	`has_many`/`has_and_belongs_to_many` associations
`country`	`select` (countries as options)	`string` with `name =~ /country/`
`time_zone`	`select` (timezones as options)	`string` with `name =~ /time_zone/`
`rich_text_area`	`trix-editor`	-

Custom inputs

It is very easy to add custom inputs to Simple Form. For instance, if you want to add a custom input that extends the string one, you just need to add this file:

# app/inputs/currency_input.rb
class CurrencyInput < SimpleForm::Inputs::Base
  def input(wrapper_options)
    merged_input_options = merge_wrapper_options(input_html_options, wrapper_options)

    "$ #{@builder.text_field(attribute_name, merged_input_options)}".html_safe
  end
end

And use it in your views:

f.input :money, as: :currency

Note, you may have to create the app/inputs/ directory and restart your webserver.

You can also redefine existing Simple Form inputs by creating a new class with the same name. For instance, if you want to wrap date/time/datetime in a div, you can do:

# app/inputs/date_time_input.rb
class DateTimeInput < SimpleForm::Inputs::DateTimeInput
  def input(wrapper_options)
    template.content_tag(:div, super)
  end
end

Or if you want to add a class to all the select fields you can do:

# app/inputs/collection_select_input.rb
class CollectionSelectInput < SimpleForm::Inputs::CollectionSelectInput
  def input_html_classes
    super.push('chosen')
  end
end

If needed, you can namespace your custom inputs in a module and tell Simple Form to look for their definitions in this module. This can avoid conflicts with other form libraries (like Formtastic) that look up the global context to find inputs definition too.

# app/inputs/custom_inputs/numeric_input
module CustomInputs
  class NumericInput < SimpleForm::Inputs::NumericInput
    def input_html_classes
      super.push('no-spinner')
    end
  end
end

And in the SimpleForm initializer :

# config/simple_form.rb
config.custom_inputs_namespaces << "CustomInputs"

Custom form builder

You can create a custom form builder that uses Simple Form.

Create a helper method that calls simple_form_for with a custom builder:

def custom_form_for(object, *args, &block)
  options = args.extract_options!
  simple_form_for(object, *(args << options.merge(builder: CustomFormBuilder)), &block)
end

Create a form builder class that inherits from SimpleForm::FormBuilder.

class CustomFormBuilder < SimpleForm::FormBuilder
  def input(attribute_name, options = {}, &block)
    super(attribute_name, options.merge(label: false), &block)
  end
end

Configuration

Simple Form has several configuration options. You can read and change them in the initializer created by Simple Form, so if you haven’t executed the command below yet, please do:

rails generate simple_form:install

The wrappers API

With Simple Form you can configure how your components will be rendered using the wrappers API. The syntax looks like this:

config.wrappers tag: :div, class: :input,
                error_class: :field_with_errors,
                valid_class: :field_without_errors do |b|

  # Form extensions
  b.use :html5
  b.optional :pattern
  b.use :maxlength
  b.use :placeholder
  b.use :readonly

  # Form components
  b.use :label_input
  b.use :hint,  wrap_with: { tag: :span, class: :hint }
  b.use :error, wrap_with: { tag: :span, class: :error }
end

The Form components will generate the form tags like labels, inputs, hints or errors contents. The available components are:

:label         # The <label> tag alone
:input         # The <input> tag alone
:label_input   # The <label> and the <input> tags
:hint          # The hint for the input
:error         # The error for the input

The Form extensions are used to generate some attributes or perform some lookups on the model to add extra information to your components.

You can create new Form components using the wrappers API as in the following example:

config.wrappers do |b|
  b.use :placeholder
  b.use :label_input
  b.wrapper tag: :div, class: 'separator' do |component|
    component.use :hint,  wrap_with: { tag: :span, class: :hint }
    component.use :error, wrap_with: { tag: :span, class: :error }
  end
end

this will wrap the hint and error components within a div tag using the class 'separator'.

You can customize Form components passing options to them:

config.wrappers do |b|
  b.use :label_input, class: 'label-input-class', error_class: 'is-invalid', valid_class: 'is-valid'
end

This sets the input and label classes to 'label-input-class' and will set the class 'is-invalid' if the input has errors and 'is-valid' if the input is valid.

If you want to customize the custom Form components on demand you can give it a name like this:

config.wrappers do |b|
  b.use :placeholder
  b.use :label_input
  b.wrapper :my_wrapper, tag: :div, class: 'separator', html: { id: 'my_wrapper_id' } do |component|
    component.use :hint,  wrap_with: { tag: :span, class: :hint }
    component.use :error, wrap_with: { tag: :span, class: :error }
  end
end

and now you can pass options to your input calls to customize the :my_wrapper Form component.

# Completely turns off the custom wrapper
f.input :name, my_wrapper: false

# Configure the html
f.input :name, my_wrapper_html: { id: 'special_id' }

# Configure the tag
f.input :name, my_wrapper_tag: :p

You can also define more than one wrapper and pick one to render in a specific form or input. To define another wrapper you have to give it a name, as the follow:

config.wrappers :small do |b|
  b.use :placeholder
  b.use :label_input
end

and use it in this way:

# Specifying to whole form
simple_form_for @user, wrapper: :small do |f|
  f.input :name
end

# Specifying to one input
simple_form_for @user do |f|
  f.input :name, wrapper: :small
end

Simple Form also allows you to use optional elements. For instance, let’s suppose you want to use hints or placeholders, but you don’t want them to be generated automatically. You can set their default values to false or use the optional method. Is preferable to use the optional syntax:

config.wrappers placeholder: false do |b|
  b.use :placeholder
  b.use :label_input
  b.wrapper tag: :div, class: 'separator' do |component|
    component.optional :hint, wrap_with: { tag: :span, class: :hint }
    component.use :error, wrap_with: { tag: :span, class: :error }
  end
end

By setting it as optional, a hint will only be generated when hint: true is explicitly used. The same for placeholder.

It is also possible to give the option :unless_blank to the wrapper if you want to render it only when the content is present.

  b.wrapper tag: :span, class: 'hint', unless_blank: true do |component|
    component.optional :hint
  end

Custom Components

When you use custom wrappers, you might also be looking for a way to add custom components to your wrapper. The default components are:

:label         # The <label> tag alone
:input         # The <input> tag alone
:label_input   # The <label> and the <input> tags
:hint          # The hint for the input
:error         # The error for the input

A custom component might be interesting for you if your views look something like this:

<%= simple_form_for @blog do |f| %>
  <div class="row">
    <div class="span1 number">
      1
    </div>
    <div class="span8">
      <%= f.input :title %>
    </div>
  </div>
  <div class="row">
    <div class="span1 number">
      2
    </div>
    <div class="span8">
      <%= f.input :body, as: :text %>
    </div>
  </div>
<% end %>

A cleaner method to create your views would be:

<%= simple_form_for @blog, wrapper: :with_numbers do |f| %>
  <%= f.input :title, number: 1 %>
  <%= f.input :body, as: :text, number: 2 %>
<% end %>

To use the number option on the input, first, tells to Simple Form the place where the components will be:

# config/initializers/simple_form.rb
Dir[Rails.root.join('lib/components/**/*.rb')].each { |f| require f }

Create a new component within the path specified above:

# lib/components/numbers_component.rb
module NumbersComponent
  # To avoid deprecation warning, you need to make the wrapper_options explicit
  # even when they won't be used.
  def number(wrapper_options = nil)
    @number ||= begin
      options[:number].to_s.html_safe if options[:number].present?
    end
  end
end

SimpleForm.include_component(NumbersComponent)

Finally, add a new wrapper to the config/initializers/simple_form.rb file:

config.wrappers :with_numbers, tag: 'div', class: 'row', error_class: 'error' do |b|
  b.use :html5
  b.use :number, wrap_with: { tag: 'div', class: 'span1 number' }
  b.wrapper tag: 'div', class: 'span8' do |ba|
    ba.use :placeholder
    ba.use :label
    ba.use :input
    ba.use :error, wrap_with: { tag: 'span', class: 'help-inline' }
    ba.use :hint,  wrap_with: { tag: 'p', class: 'help-block' }
  end
end

Using non Active Record objects

There are few ways to build forms with objects that don’t inherit from Active Record, as follows:

You can include the module ActiveModel::Model.

class User
  include ActiveModel::Model

  attr_accessor :id, :name
end

If you are using Presenters or Decorators that inherit from SimpleDelegator you can delegate it to the model.

class UserPresenter < SimpleDelegator
  # Without that, Simple Form will consider the user model as the object.
  def to_model
    self
  end
end

You can define all methods required by the helpers.

class User
  extend ActiveModel::Naming

  attr_accessor :id, :name

  def to_model
    self
  end

  def to_key
    id
  end

  def persisted?
    false
  end
end

To have SimpleForm infer the attributes’ types, you can provide #has_attribute? and #type_for_attribute methods. The later should return an object that responds to #type with the attribute type. This is useful for generating the correct input types (eg: checkboxes for booleans).

class User < Struct.new(:id, :name, :age, :registered)
  def to_model
    self
  end

  def model_name
    OpenStruct.new(param_key: "user")
  end

  def to_key
    id
  end

  def persisted?
    id.present?
  end

  def has_attribute?(attr_name)
    %w(id name age registered).include?(attr_name.to_s)
  end

  def type_for_attribute(attr_name)
    case attr_name.to_s
      when "id" then OpenStruct.new(type: :integer)
      when "name" then OpenStruct.new(type: :string)
      when "age" then OpenStruct.new(type: :integer)
      when "registered" then OpenStruct.new(type: :boolean)
    end
  end
end

If your object doesn’t implement those methods, you must make explicit it when you are building the form

class User
  attr_accessor :id, :name

  # The only method required to use the f.submit helper.
  def persisted?
    false
  end
end

<%= simple_form_for(@user, as: :user, method: :post, url: users_path) do |f| %>
  <%= f.input :name %>
  <%= f.submit 'New user' %>
<% end %>

Information

RDocs

You can view the Simple Form documentation in RDoc format here:

http://rubydoc.info/github/heartcombo/simple_form/main/frames

Bug reports

If you discover any bugs, feel free to create an issue on GitHub. Please add as much information as possible to help us in fixing the potential bug. We also encourage you to help even more by forking and sending us a pull request.

https://github.com/heartcombo/simple_form/issues

If you have discovered a security related bug, please do NOT use the GitHub issue tracker. Send an e-mail to heartcombo@googlegroups.com.

Maintainers

Carlos Antonio da Silva (https://github.com/carlosantoniodasilva)
Rafael Mendonça França (https://github.com/rafaelfranca)
Felipe Renan (https://github.com/feliperenan)