How do I have optional nested resources submitted through a form in Rails 3?

Iam using simple_form. The user can create a message. Optionally, they can attach a contact. Right now, if they don't attach a contact, a new Con开发者_Python百科tact is still created?

How can I only associate and create a new Contact when that Contact portion of the form is filled out?

Here is the form I use now:

1 = simple_form_for @message, :remote => true do |f|
  2   #message_form
  3     = f.error_messages
  4     %p
  5       = f.input :account_name, :url => autocomplete_account_name_messages_path, :size => 40, :as => :autocomplete
  6     %p
  7       = f.input :subject
  8       %br 
  9       = f.input :body, :as => :text, :input_html => { :class => 'autogrow', :rows => 5, :cols => 30, :maxlength => 140  }
 10     = hidden_field_tag :sender_id, params[:sender_id]
 11     = hidden_field_tag :receiver_id, params[:id]
 12 
 13     = f.submit 'Give'
 14     = f.submit 'Request'
 15     
 16     #add_contact_btn
 17       = link_to "Add Contact"
 18     
 19       #contact_form
 20         = simple_fields_for :contact do |fc|
 21           %p
 22             = fc.input :first_name
 23           %p
 24             = fc.input :last_name
 25             = fc.input :email
 26             = fc.input :title
 27             = fc.input :office_phone

---

This should be done in your model, something like:

accepts_nested_attributes_for :contact, :allow_destroy => true, :reject_if => lambda { |c| c[:first_name].blank? && c[:last_name].blank? }

Or whatever condition you prefer.

The dirty way, while Rails bugs are being fixed. In your model:

after_save :check_nil_contact

def check_nil_contact
  if contact.first_name.blank?
    contact.destroy
  end
end