Class: ActionView::Helpers::FormBuilder

Alias for #multipart.

Returns a checkbox tag tailored for accessing a specified attribute (identified by method) on an object assigned to the template (identified by #object). This object must be an instance object (@object) and not a local object. It’s intended that method returns an integer and if that integer is above zero, then the checkbox is checked. Additional options on the input tag can be passed as a hash with #options. The checked_value defaults to 1 while the default unchecked_value is set to 0 which is convenient for boolean values.

Options

• Any standard HTML attributes for the tag can be passed in, for example :class.

• :checked - true or false forces the state of the checkbox to be checked or not.

• :include_hidden - If set to false, the auxiliary hidden field described below will not be generated.

Gotcha

The HTML specification says unchecked check boxes are not successful, and thus web browsers do not send them. Unfortunately this introduces a gotcha: if an Invoice model has a paid flag, and in the form that edits a paid invoice the user unchecks its check box, no paid parameter is sent. So, any mass-assignment idiom like

@invoice.update(params[:invoice])

wouldn’t update the flag.

To prevent this the helper generates an auxiliary hidden field before every check box. The hidden field has the same name and its attributes mimic an unchecked check box.

This way, the client either sends only the hidden field (representing the check box is unchecked), or both fields. Since the HTML specification says key/value pairs have to be sent in the same order they appear in the form, and parameters extraction gets the last occurrence of any repeated key in the query string, that works for ordinary forms.

Unfortunately that workaround does not work when the check box goes within an array-like parameter, as in

<%= fields_for "project[invoice_attributes][]", invoice, index: nil do |form| %>
  <%= form.check_box :paid %>
  ...
<% end %>

because parameter name repetition is precisely what Rails seeks to distinguish the elements of the array. For each item with a checked check box you get an extra ghost item with only that attribute, assigned to “0”.

In that case it is preferable to either use check_box_tag or to use hashes instead of arrays.

Examples

# Let's say that @post.validated? is 1:
check_box("validated")
# => <input name="post[validated]" type="hidden" value="0" />
#    <input checked="checked" type="checkbox" id="post_validated" name="post[validated]" value="1" />

# Let's say that @puppy.gooddog is "no":
check_box("gooddog", {}, "yes", "no")
# => <input name="puppy[gooddog]" type="hidden" value="no" />
#    <input type="checkbox" id="puppy_gooddog" name="puppy[gooddog]" value="yes" />

# Let's say that @eula.accepted is "no":
check_box("accepted", { class: 'eula_check' }, "yes", "no")
# => <input name="eula[accepted]" type="hidden" value="no" />
#    <input type="checkbox" class="eula_check" id="eula_accepted" name="eula[accepted]" value="yes" />

Wraps FormOptionsHelper#collection_check_boxes for form builders:

<%= form_for @post do |f| %>
  <%= f.collection_check_boxes :author_ids, Author.all, :id, :name_with_initial %>
  <%= f.submit %>
<% end %>

Please refer to the documentation of the base helper for details.

Wraps FormOptionsHelper#collection_radio_buttons for form builders:

<%= form_for @post do |f| %>
  <%= f.collection_radio_buttons :author_id, Author.all, :id, :name_with_initial %>
  <%= f.submit %>
<% end %>

Please refer to the documentation of the base helper for details.

Wraps FormOptionsHelper#collection_select for form builders:

<%= form_for @post do |f| %>
  <%= f.collection_select :person_id, Author.all, :id, :name_with_initial, prompt: true %>
  <%= f.submit %>
<% end %>

Please refer to the documentation of the base helper for details.

Wraps FormHelper#color_field for form builders:

<%= form_with model: @user do |f| %>
  <%= f.color_field :favorite_color %>
<% end %>

Please refer to the documentation of the base helper for details.

Wraps FormHelper#date_field for form builders:

<%= form_with model: @user do |f| %>
  <%= f.date_field :born_on %>
<% end %>

Please refer to the documentation of the base helper for details.

Wraps DateHelper#date_select for form builders:

<%= form_for @person do |f| %>
  <%= f.date_select :birth_date %>
  <%= f.submit %>
<% end %>

Please refer to the documentation of the base helper for details.

Wraps FormHelper#datetime_field for form builders:

<%= form_with model: @user do |f| %>
  <%= f.datetime_field :graduation_day %>
<% end %>

Please refer to the documentation of the base helper for details.

Wraps FormHelper#datetime_local_field for form builders:

<%= form_with model: @user do |f| %>
  <%= f.datetime_local_field :graduation_day %>
<% end %>

Please refer to the documentation of the base helper for details.

Wraps DateHelper#datetime_select for form builders:

<%= form_for @person do |f| %>
  <%= f.datetime_select :last_request_at %>
  <%= f.submit %>
<% end %>

Please refer to the documentation of the base helper for details.

Wraps FormHelper#email_field for form builders:

<%= form_with model: @user do |f| %>
  <%= f.email_field :address %>
<% end %>

Please refer to the documentation of the base helper for details.

Generate an HTML #id attribute value for the given field

Return the value generated by the FormBuilder for the given attribute name.

<%= form_for @post do |f| %>
  <%= f.label :title %>
  <%= f.text_field :title, aria: { describedby: f.field_id(:title, :error) } %>
  <%= tag.span("is blank", id: f.field_id(:title, :error) %>
<% end %>

In the example above, the <input type="text"> element built by the call to #text_field declares an aria-describedby attribute referencing the <span> element, sharing a common #id root (post_title, in this case).

Generate an HTML name attribute value for the given name and field combination

Return the value generated by the FormBuilder for the given attribute name.

<%= form_for @post do |f| %>
  <%= f.text_field :title, name: f.field_name(:title, :subtitle) %>
  <%# => <input type="text" name="post[title][subtitle]"> %>
<% end %>

<%= form_for @post do |f| %>
  <%= f.text_field :tag, name: f.field_name(:tag, multiple: true) %>
  <%# => <input type="text" name="post[tag][]"> %>
<% end %>

See the docs for the FormHelper#fields helper method.

Creates a scope around a specific model object like form_for, but doesn’t create the form tags themselves. This makes fields_for suitable for specifying additional model objects in the same form.

Although the usage and purpose of fields_for is similar to form_for‘s, its method signature is slightly different. Like form_for, it yields a FormBuilder object associated with a particular model object to a block, and within the block allows methods to be called on the builder to generate fields associated with the model object. Fields may reflect a model object in two ways - how they are named (hence how submitted values appear within the params hash in the controller) and what default values are shown when the form the fields appear in is first displayed. In order for both of these features to be specified independently, both an object name (represented by either a symbol or string) and the object itself can be passed to the method separately -

<%= form_for @person do |person_form| %>
  First name: <%= person_form.text_field :first_name %>
  Last name : <%= person_form.text_field :last_name %>

  <%= fields_for :permission, @person.permission do |permission_fields| %>
    Admin?  : <%= permission_fields.check_box :admin %>
  <% end %>

  <%= person_form.submit %>
<% end %>

In this case, the checkbox field will be represented by an HTML input tag with the name attribute permission[admin], and the submitted value will appear in the controller as params[:permission][:admin]. If @person.permission is an existing record with an attribute admin, the initial state of the checkbox when first displayed will reflect the value of @person.permission.admin.

Often this can be simplified by passing just the name of the model object to fields_for -

<%= fields_for :permission do |permission_fields| %>
  Admin?: <%= permission_fields.check_box :admin %>
<% end %>

…in which case, if :permission also happens to be the name of an instance variable @permission, the initial state of the input field will reflect the value of that variable’s attribute @permission.admin.

Alternatively, you can pass just the model object itself (if the first argument isn’t a string or symbol fields_for will realize that the name has been omitted) -

<%= fields_for @person.permission do |permission_fields| %>
  Admin?: <%= permission_fields.check_box :admin %>
<% end %>

and fields_for will derive the required name of the field from the class of the model object, e.g. if @person.permission, is of class Permission, the field will still be named permission[admin].

Note: This also works for the methods in FormOptionsHelper and DateHelper that are designed to work with an object as base, like FormOptionsHelper#collection_select and DateHelper#datetime_select.

fields_for tries to be smart about parameters, but it can be confused if both name and value parameters are provided and the provided value has the shape of an option ::Hash. To remove the ambiguity, explicitly pass an option ::Hash, even if empty.

<%= form_for @person do |person_form| %>
  ...
  <%= fields_for :permission, @person.permission, {} do |permission_fields| %>
    Admin?: <%= check_box_tag permission_fields.field_name(:admin), @person.permission[:admin] %>
  <% end %>
  ...
<% end %>

Nested Attributes Examples

When the object belonging to the current scope has a nested attribute writer for a certain attribute, fields_for will yield a new scope for that attribute. This allows you to create forms that set or change the attributes of a parent object and its associations in one go.

Nested attribute writers are normal setter methods named after an association. The most common way of defining these writers is either with accepts_nested_attributes_for in a model definition or by defining a method with the proper name. For example: the attribute writer for the association :address is called address_attributes=.

Whether a one-to-one or one-to-many style form builder will be yielded depends on whether the normal reader method returns a single object or an array of objects.

One-to-one

Consider a Person class which returns a single Address from the address reader method and responds to the address_attributes= writer method:

class Person
  def address
    @address
  end

  def address_attributes=(attributes)
    # Process the attributes hash
  end
end

This model can now be used with a nested fields_for, like so:

<%= form_for @person do |person_form| %>
  ...
  <%= person_form.fields_for :address do |address_fields| %>
    Street  : <%= address_fields.text_field :street %>
    Zip code: <%= address_fields.text_field :zip_code %>
  <% end %>
  ...
<% end %>

When address is already an association on a Person you can use accepts_nested_attributes_for to define the writer method for you:

class Person < ActiveRecord::Base
  has_one :address
  accepts_nested_attributes_for :address
end

If you want to destroy the associated model through the form, you have to enable it first using the :allow_destroy option for accepts_nested_attributes_for:

class Person < ActiveRecord::Base
  has_one :address
  accepts_nested_attributes_for :address, allow_destroy: true
end

Now, when you use a form element with the _destroy parameter, with a value that evaluates to true, you will destroy the associated model (e.g. 1, ‘1’, true, or ‘true’):

<%= form_for @person do |person_form| %>
  ...
  <%= person_form.fields_for :address do |address_fields| %>
    ...
    Delete: <%= address_fields.check_box :_destroy %>
  <% end %>
  ...
<% end %>

One-to-many

Consider a Person class which returns an array of Project instances from the projects reader method and responds to the projects_attributes= writer method:

class Person
  def projects
    [@project1, @project2]
  end

  def projects_attributes=(attributes)
    # Process the attributes hash
  end
end

Note that the projects_attributes= writer method is in fact required for fields_for to correctly identify :projects as a collection, and the correct indices to be set in the form markup.

When projects is already an association on Person you can use accepts_nested_attributes_for to define the writer method for you:

class Person < ActiveRecord::Base
  has_many :projects
  accepts_nested_attributes_for :projects
end

This model can now be used with a nested fields_for. The block given to the nested fields_for call will be repeated for each instance in the collection:

<%= form_for @person do |person_form| %>
  ...
  <%= person_form.fields_for :projects do |project_fields| %>
    <% if project_fields.object.active? %>
      Name: <%= project_fields.text_field :name %>
    <% end %>
  <% end %>
  ...
<% end %>

It’s also possible to specify the instance to be used:

<%= form_for @person do |person_form| %>
  ...
  <% @person.projects.each do |project| %>
    <% if project.active? %>
      <%= person_form.fields_for :projects, project do |project_fields| %>
        Name: <%= project_fields.text_field :name %>
      <% end %>
    <% end %>
  <% end %>
  ...
<% end %>

Or a collection to be used:

<%= form_for @person do |person_form| %>
  ...
  <%= person_form.fields_for :projects, @active_projects do |project_fields| %>
    Name: <%= project_fields.text_field :name %>
  <% end %>
  ...
<% end %>

If you want to destroy any of the associated models through the form, you have to enable it first using the :allow_destroy option for accepts_nested_attributes_for:

class Person < ActiveRecord::Base
  has_many :projects
  accepts_nested_attributes_for :projects, allow_destroy: true
end

This will allow you to specify which models to destroy in the attributes hash by adding a form element for the _destroy parameter with a value that evaluates to true (e.g. 1, ‘1’, true, or ‘true’):

<%= form_for @person do |person_form| %>
  ...
  <%= person_form.fields_for :projects do |project_fields| %>
    Delete: <%= project_fields.check_box :_destroy %>
  <% end %>
  ...
<% end %>

When a collection is used you might want to know the index of each object in the array. For this purpose, the #index method is available in the FormBuilder object.

<%= form_for @person do |person_form| %>
  ...
  <%= person_form.fields_for :projects do |project_fields| %>
    Project #<%= project_fields.index %>
    ...
  <% end %>
  ...
<% end %>

Note that fields_for will automatically generate a hidden field to store the ID of the record. There are circumstances where this hidden field is not needed and you can pass include_id: false to prevent fields_for from rendering it automatically.

Returns a file upload input tag tailored for accessing a specified attribute (identified by method) on an object assigned to the template (identified by #object). Additional options on the input tag can be passed as a hash with #options. These options will be tagged onto the HTML as an HTML element attribute as in the example shown.

Using this method inside a form_with block will set the enclosing form’s encoding to multipart/form-data.

Options

• Creates standard HTML attributes for the tag.

• :disabled - If set to true, the user will not be able to use this input.

• :multiple - If set to true, *in most updated browsers* the user will be allowed to select multiple files.

• :include_hidden - When multiple: true and include_hidden: true, the field will be prefixed with an <input type="hidden"> field with an empty value to support submitting an empty collection of files. Since include_hidden will default to config.active_storage.multiple_file_field_include_hidden if you don’t specify include_hidden, you will need to pass include_hidden: false to prevent submitting an empty collection of files when passing multiple: true.

• :accept - If set to one or multiple mime-types, the user will be suggested a filter when choosing a file. You still need to set up model validations.

Examples

# Let's say that @user has avatar:
file_field(:avatar)
# => <input type="file" id="user_avatar" name="user[avatar]" />

# Let's say that @post has image:
file_field(:image, :multiple => true)
# => <input type="file" id="post_image" name="post[image][]" multiple="multiple" />

# Let's say that @post has attached:
file_field(:attached, accept: 'text/html')
# => <input accept="text/html" type="file" id="post_attached" name="post[attached]" />

# Let's say that @post has image:
file_field(:image, accept: 'image/png,image/gif,image/jpeg')
# => <input type="file" id="post_image" name="post[image]" accept="image/png,image/gif,image/jpeg" />

# Let's say that @attachment has file:
file_field(:file, class: 'file_input')
# => <input type="file" id="attachment_file" name="attachment[file]" class="file_input" />

Wraps FormOptionsHelper#grouped_collection_select for form builders:

<%= form_for @city do |f| %>
  <%= f.grouped_collection_select :country_id, @continents, :countries, :name, :id, :name %>
  <%= f.submit %>
<% end %>

Please refer to the documentation of the base helper for details.

Returns a hidden input tag tailored for accessing a specified attribute (identified by method) on an object assigned to the template (identified by #object). Additional options on the input tag can be passed as a hash with #options. These options will be tagged onto the HTML as an HTML element attribute as in the example shown.

Examples

# Let's say that @signup.pass_confirm returns true:
hidden_field(:pass_confirm)
# => <input type="hidden" id="signup_pass_confirm" name="signup[pass_confirm]" value="true" />

# Let's say that @post.tag_list returns "blog, ruby":
hidden_field(:tag_list)
# => <input type="hidden" id="post_tag_list" name="post[tag_list]" value="blog, ruby" />

# Let's say that @user.token returns "abcde":
hidden_field(:token)
# => <input type="hidden" id="user_token" name="user[token]" value="abcde" />

Generate an HTML id attribute value.

return the <form> element’s id attribute.

<%= form_for @post do |f| %>
  <%# ... %>

  <% content_for :sticky_footer do %>
    <%= form.button(form: f.id) %>
  <% end %>
<% end %>

In the example above, the :sticky_footer content area will exist outside of the <form> element. By declaring the form HTML attribute, we hint to the browser that the generated <button> element should be treated as the <form> element’s submit button, regardless of where it exists in the DOM.

Returns a label tag tailored for labelling an input field for a specified attribute (identified by method) on an object assigned to the template (identified by #object). The text of label will default to the attribute name unless a translation is found in the current ::I18n locale (through helpers.label.<modelname>.<attribute>) or you specify it explicitly. Additional options on the label tag can be passed as a hash with #options. These options will be tagged onto the HTML as an HTML element attribute as in the example shown, except for the :value option, which is designed to target labels for radio_button tags (where the value is used in the ID of the input tag).

Examples

label(:title)
# => <label for="post_title">Title</label>

You can localize your labels based on model and attribute names. For example you can define the following in your locale (e.g. en.yml)

helpers:
  label:
    post:
      body: "Write your entire text here"

Which then will result in

label(:body)
# => <label for="post_body">Write your entire text here</label>

Localization can also be based purely on the translation of the attribute-name (if you are using ::ActiveRecord):

activerecord:
  attributes:
    post:
      cost: "Total cost"

label(:cost)
# => <label for="post_cost">Total cost</label>

label(:title, "A short title")
# => <label for="post_title">A short title</label>

label(:title, "A short title", class: "title_label")
# => <label for="post_title" class="title_label">A short title</label>

label(:privacy, "Public Post", value: "public")
# => <label for="post_privacy_public">Public Post</label>

label(:cost) do |translation|
  content_tag(:span, translation, class: "cost_label")
end
# => <label for="post_cost"><span class="cost_label">Total cost</span></label>

label(:cost) do |builder|
  content_tag(:span, builder.translation, class: "cost_label")
end
# => <label for="post_cost"><span class="cost_label">Total cost</span></label>

label(:cost) do |builder|
  content_tag(:span, builder.translation, class: [
    "cost_label",
    ("error_label" if builder.object.errors.include?(:cost))
  ])
end
# => <label for="post_cost"><span class="cost_label error_label">Total cost</span></label>

label(:terms) do
  raw('Accept <a href="/terms">Terms</a>.')
end
# => <label for="post_terms">Accept <a href="/terms">Terms</a>.</label>

Wraps FormHelper#month_field for form builders:

<%= form_with model: @user do |f| %>
  <%= f.month_field :birthday_month %>
<% end %>

Please refer to the documentation of the base helper for details.

Wraps FormHelper#number_field for form builders:

<%= form_with model: @user do |f| %>
  <%= f.number_field :age %>
<% end %>

Please refer to the documentation of the base helper for details.

Wraps FormHelper#password_field for form builders:

<%= form_with model: @user do |f| %>
  <%= f.password_field :password %>
<% end %>

Please refer to the documentation of the base helper for details.

Wraps FormHelper#phone_field for form builders:

<%= form_with model: @user do |f| %>
  <%= f.phone_field :phone %>
<% end %>

Please refer to the documentation of the base helper for details.

Returns a radio button tag for accessing a specified attribute (identified by method) on an object assigned to the template (identified by #object). If the current value of method is tag_value the radio button will be checked.

To force the radio button to be checked pass checked: true in the #options hash. You may pass HTML options there as well.

# Let's say that @post.category returns "rails":
radio_button("category", "rails")
radio_button("category", "java")
# => <input type="radio" id="post_category_rails" name="post[category]" value="rails" checked="checked" />
#    <input type="radio" id="post_category_java" name="post[category]" value="java" />

# Let's say that @user.receive_newsletter returns "no":
radio_button("receive_newsletter", "yes")
radio_button("receive_newsletter", "no")
# => <input type="radio" id="user_receive_newsletter_yes" name="user[receive_newsletter]" value="yes" />
#    <input type="radio" id="user_receive_newsletter_no" name="user[receive_newsletter]" value="no" checked="checked" />

Wraps FormHelper#range_field for form builders:

<%= form_with model: @user do |f| %>
  <%= f.range_field :age %>
<% end %>

Please refer to the documentation of the base helper for details.

Wraps FormHelper#search_field for form builders:

<%= form_with model: @user do |f| %>
  <%= f.search_field :name %>
<% end %>

Please refer to the documentation of the base helper for details.

Wraps FormOptionsHelper#select for form builders:

<%= form_for @post do |f| %>
  <%= f.select :person_id, Person.all.collect { |p| [ p.name, p.id ] }, include_blank: true %>
  <%= f.submit %>
<% end %>

Please refer to the documentation of the base helper for details.

Add the submit button for the given form. When no value is given, it checks if the object is a new resource or not to create the proper label:

<%= form_for @post do |f| %>
  <%= f.submit %>
<% end %>

In the example above, if @post is a new record, it will use “Create Post” as submit button label; otherwise, it uses “Update Post”.

Those labels can be customized using ::I18n under the helpers.submit key and using %{model} for translation interpolation:

en:
  helpers:
    submit:
      create: "Create a %{model}"
      update: "Confirm changes to %{model}"

It also searches for a key specific to the given object:

en:
  helpers:
    submit:
      post:
        create: "Add %{model}"

Wraps FormHelper#telephone_field for form builders:

<%= form_with model: @user do |f| %>
  <%= f.telephone_field :phone %>
<% end %>

Please refer to the documentation of the base helper for details.

Wraps FormHelper#text_area for form builders:

<%= form_with model: @user do |f| %>
  <%= f.text_area :detail %>
<% end %>

Please refer to the documentation of the base helper for details.

Wraps FormHelper#text_field for form builders:

<%= form_with model: @user do |f| %>
  <%= f.text_field :name %>
<% end %>

Please refer to the documentation of the base helper for details.

Wraps FormHelper#time_field for form builders:

<%= form_with model: @user do |f| %>
  <%= f.time_field :born_at %>
<% end %>

Please refer to the documentation of the base helper for details.

Wraps DateHelper#time_select for form builders:

<%= form_for @race do |f| %>
  <%= f.time_select :average_lap %>
  <%= f.submit %>
<% end %>

Please refer to the documentation of the base helper for details.

Wraps FormOptionsHelper#time_zone_select for form builders:

<%= form_for @user do |f| %>
  <%= f.time_zone_select :time_zone, nil, include_blank: true %>
  <%= f.submit %>
<% end %>

Please refer to the documentation of the base helper for details.

Wraps FormHelper#url_field for form builders:

<%= form_with model: @user do |f| %>
  <%= f.url_field :homepage %>
<% end %>

Please refer to the documentation of the base helper for details.

Wraps FormHelper#week_field for form builders:

<%= form_with model: @user do |f| %>
  <%= f.week_field :birthday_week %>
<% end %>

Please refer to the documentation of the base helper for details.

Wraps FormOptionsHelper#weekday_select for form builders:

<%= form_for @user do |f| %>
  <%= f.weekday_select :weekday, include_blank: true %>
  <%= f.submit %>
<% end %>

Please refer to the documentation of the base helper for details.