Module ActionView::Helpers::FormHelper

Returns a checkbox tag tailored for accessing a specified attribute (identified by method) on an object assigned to the template (identified by 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. Usually unchecked checkboxes don’t post anything. We work around this problem by adding a hidden value with the same name as the checkbox.

Example (call, result). Imagine that @post.validated? returns 1:

check_box("post", "validated")
  <input type="checkbox" id="post_validate" name="post[validated]" value="1" checked="checked" />
  <input name="post[validated]" type="hidden" value="0" />

Example (call, result). Imagine that @puppy.gooddog returns no:

check_box("puppy", "gooddog", {}, "yes", "no")
  <input type="checkbox" id="puppy_gooddog" name="puppy[gooddog]" value="yes" />
  <input name="puppy[gooddog]" type="hidden" value="no" />

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. Example:

<% form_for :person, @person, :url => { :action => "update" } 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 %>
<% end %>

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

Works just like #text_field, but returns an input tag of the “file” type instead, which won’t have a default value.

Creates a form and a scope around a specific model object, which is then used as a base for questioning about values for the fields. Examples:

<% form_for :person, @person, :url => { :action => "update" } do |f| %>
  First name: <%= f.text_field :first_name %>
  Last name : <%= f.text_field :last_name %>
  Biography : <%= f.text_area :biography %>
  Admin?    : <%= f.check_box :admin %>
<% end %>

Worth noting is that the #form_for tag is called in a ERb evaluation block, not a ERb output block. So that’s <% %>, not <%= %>. Also worth noting is that the #form_for yields a form_builder object, in this example as f, which emulates the API for the stand-alone FormHelper methods, but without the object name. So instead of text_field :person, :name, you get away with f.text_field :name.

That in itself is a modest increase in comfort. The big news is that #form_for allows us to more easily escape the instance variable convention, so while the stand-alone approach would require text_field :person, :name, :object => person to work with local variables instead of instance ones, the #form_for calls remain the same. You simply declare once with :person, person and all subsequent field calls save :person and :object => person.

Also note that #form_for doesn’t create an exclusive scope. It’s still possible to use both the stand-alone FormHelper methods and methods from FormTagHelper. Example:

<% form_for :person, @person, :url => { :action => "update" } do |f| %>
  First name: <%= f.text_field :first_name %>
  Last name : <%= f.text_field :last_name %>
  Biography : <%= text_area :person, :biography %>
  Admin?    : <%= check_box_tag "person[admin]", @person.company.admin? %>
<% end %>

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

Html attributes for the form tag can be given as :html => {…}. Example:

<% form_for :person, @person, :html => {:id => 'person_form'} do |f| %>
  ...
<% end %>

You can also build forms using a customized FormBuilder class. Subclass FormBuilder and override or define some more helpers, then use your custom builder like so:

<% form_for :person, @person, :url => { :action => "update" }, :builder => LabellingFormBuilder do |f| %>
  <%= f.text_field :first_name %>
  <%= f.text_field :last_name %>
  <%= text_area :person, :biography %>
  <%= check_box_tag "person[admin]", @person.company.admin? %>
<% end %>

In many cases you will want to wrap the above in another helper, such as:

def labelled_form_for(name, object, options, &proc)
  form_for(name, object, options.merge(:builder => LabellingFormBuiler), &proc)
end

Works just like #text_field, but returns an input tag of the “hidden” type instead.

Works just like #text_field, but returns an input tag of the “password” type instead.

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. Additional options on the input tag can be passed as a hash with options. Example (call, result). Imagine that @post.category returns “rails”:

radio_button("post", "category", "rails")
radio_button("post", "category", "java")
  <input type="radio" id="post_category" name="post[category]" value="rails" checked="checked" />
  <input type="radio" id="post_category" name="post[category]" value="java" />

Returns a textarea opening and closing tag set 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.

Example (call, result):

text_area("post", "body", "cols" => 20, "rows" => 40)
  <textarea cols="20" rows="40" id="post_body" name="post[body]">
    #{@post.body}
  <%rtextarea>

Returns an input tag of the “text” type 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.

Examples (call, result):

text_field("post", "title", "size" => 20)
  <input type="text" id="post_title" name="post[title]" size="20" value="#{@post.title}" />