A FormBuilder
object is associated with a particular model
object and allows you to generate fields associated with the model object.
The FormBuilder
object is yielded when using
form_for
or fields_for
. For example:
<%= form_for @person do |person_form| %>
Name: <%= person_form.text_field :name %>
Admin: <%= person_form.check_box :admin %>
<% end %>
In the above block, a FormBuilder
object is yielded as the
person_form
variable. This allows you to generate the
text_field
and check_box
fields by specifying
their eponymous methods, which modify the underlying template and
associates the +@person+ model object with the form.
The FormBuilder
object can be thought of as serving as a proxy
for the methods in the FormHelper
module. This class, however,
allows you to call methods with the model object you are building the form
for.
You can create your own custom FormBuilder templates by subclassing this class. For example:
class MyFormBuilder < ActionView::Helpers::FormBuilder
def div_radio_button(method, tag_value, options = {})
@template.content_tag(:div,
@template.radio_button(
@object_name, method, tag_value, objectify_options(options)
)
)
end
end
The above code creates a new method div_radio_button
which
wraps a div around the new radio button. Note that when options are passed
in, you must call objectify_options
in order for the model
object to get correctly passed to the method. If
objectify_options
is not called, then the newly created helper
will not be linked back to the model.
The div_radio_button
code from above can now be used as
follows:
<%= form_for @person, :builder => MyFormBuilder do |f| %>
I am a child: <%= f.div_radio_button(:admin, "child") %>
I am an adult: <%= f.div_radio_button(:admin, "adult") %>
<% end -%>
The standard set of helper methods for form building are located in the
field_helpers
class attribute.
- #
- B
- C
- E
- F
- G
- H
- L
- M
- N
- R
- S
- T
[R] | index | |
[R] | multipart | |
[R] | multipart? | |
[RW] | object | |
[RW] | object_name | |
[RW] | options |
# File actionview/lib/action_view/helpers/form_helper.rb, line 1673 def initialize(object_name, object, template, options) @nested_child_index = {} @object_name, @object, @template, @options = object_name, object, template, options @default_options = @options ? @options.slice(:index, :namespace, :skip_default_ids, :allow_method_names_outside_object) : {} convert_to_legacy_options(@options) if @object_name.to_s.match(/\[\]$/) if (object ||= @template.instance_variable_get("@#{Regexp.last_match.pre_match}")) && object.respond_to?(:to_param) @auto_index = object.to_param else raise ArgumentError, "object[] naming but object param and @object var don't exist or don't respond to to_param: #{object.inspect}" end end @multipart = nil @index = options[:index] || options[:child_index] end
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.button %>
<% end %>
In the example above, if @post is a new record, it will use “Create Post” as button label, otherwise, it uses “Update Post”.
Those labels can be customized using I18n, under the helpers.submit key (the same as submit helper) and accept the %{model} as translation interpolation:
en:
helpers:
submit:
create: "Create a %{model}"
update: "Confirm changes to %{model}"
It also searches for a key specific for the given object:
en:
helpers:
submit:
post:
create: "Add %{model}"
Examples
button("Create post")
# => <button name='button' type='submit'>Create post</button>
button do
content_tag(:strong, 'Ask me!')
end
# => <button name='button' type='submit'>
# <strong>Ask me!</strong>
# </button>
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.
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 the very 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.
# 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 ActionView::Helpers::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.
# File actionview/lib/action_view/helpers/form_options_helper.rb, line 864 def collection_check_boxes(method, collection, value_method, text_method, options = {}, html_options = {}, &block) @template.collection_check_boxes(@object_name, method, collection, value_method, text_method, objectify_options(options), @default_options.merge(html_options), &block) end
Wraps ActionView::Helpers::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 ActionView::Helpers::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.
# File actionview/lib/action_view/helpers/form_options_helper.rb, line 828 def collection_select(method, collection, value_method, text_method, options = {}, html_options = {}) @template.collection_select(@object_name, method, collection, value_method, text_method, objectify_options(options), @default_options.merge(html_options)) end
Source: on GitHub
|See the docs for the ActionView::FormHelper.fields
helper
method.
# File actionview/lib/action_view/helpers/form_helper.rb, line 1983 def fields(scope = nil, model: nil, **options, &block) options[:allow_method_names_outside_object] = true options[:skip_default_ids] = true convert_to_legacy_options(options) fields_for(scope || model, model, **options, &block) end
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 FormOptionHelper and DateHelper that are designed to work with an object as base, like FormOptionHelper#collection_select and ActionView::Helpers::DateHelper#datetime_select.
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 (eg. 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
(eg. 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
into 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.
# File actionview/lib/action_view/helpers/form_helper.rb, line 1945 def fields_for(record_name, record_object = nil, fields_options = {}, &block) fields_options, record_object = record_object, nil if record_object.is_a?(Hash) && record_object.extractable_options? fields_options[:builder] ||= options[:builder] fields_options[:namespace] = options[:namespace] fields_options[:parent_builder] = self case record_name when String, Symbol if nested_attributes_association?(record_name) return fields_for_with_nested_attributes(record_name, record_object, fields_options, block) end else record_object = record_name.is_a?(Array) ? record_name.last : record_name record_name = model_name_from_record_or_class(record_object).param_key end object_name = @object_name index = if options.has_key?(:index) options[:index] elsif defined?(@auto_index) object_name = object_name.to_s.sub(/\[\]$/, "") @auto_index end record_name = if index "#{object_name}[#{index}][#{record_name}]" elsif record_name.to_s.end_with?("[]") record_name = record_name.to_s.sub(/(.*)\[\]$/, "[\\1][#{record_object.id}]") "#{object_name}#{record_name}" else "#{object_name}[#{record_name}]" end fields_options[:child_index] = index @template.fields_for(record_name, record_object, fields_options, &block) end
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_for
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. -
: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 ActionView::Helpers::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.
# File actionview/lib/action_view/helpers/form_options_helper.rb, line 840 def grouped_collection_select(method, collection, group_method, group_label_method, option_key_method, option_value_method, options = {}, html_options = {}) @template.grouped_collection_select(@object_name, method, collection, group_method, group_label_method, option_key_method, option_value_method, objectify_options(options), @default_options.merge(html_options)) end
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" />
Source: on GitHub
|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(:terms) do
raw('Accept <a href="/terms">Terms</a>.')
end
# => <label for="post_terms">Accept <a href="/terms">Terms</a>.</label>
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 ActionView::Helpers::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.
# File actionview/lib/action_view/helpers/form_options_helper.rb, line 816 def select(method, choices = nil, options = {}, html_options = {}, &block) @template.select(@object_name, method, choices, objectify_options(options), @default_options.merge(html_options), &block) end
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 accept the %{model} as translation interpolation:
en:
helpers:
submit:
create: "Create a %{model}"
update: "Confirm changes to %{model}"
It also searches for a key specific for the given object:
en:
helpers:
submit:
post:
create: "Add %{model}"
Wraps ActionView::Helpers::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.
# File actionview/lib/action_view/helpers/form_options_helper.rb, line 852 def time_zone_select(method, priority_zones = nil, options = {}, html_options = {}) @template.time_zone_select(@object_name, method, priority_zones, objectify_options(options), @default_options.merge(html_options)) end