class Organisation < ActiveRecord::Base

  has_many    :people
  has_one     :address,:as         => :addressable,:dependent  => :destroy
  accepts_nested_attributes_for :address,:allow_destroy => true

end

class Person < ActiveRecord::Base

  attr_accessible :first_name,:last_name,:email,:organisation_id,:address_attributes

  belongs_to  :user
  belongs_to  :organisation
  has_one     :address,:allow_destroy => true

  # These two methods seem to have no effect at all!
  validates_presence_of :organisation,:unless => "address.present?"
  validates_associated  :address,:unless => "organisation.present?"

end

class Address < ActiveRecord::Base

  belongs_to :addressable,:polymorphic => true

  validates_presence_of :line1,:line2,:city,:zip

end

……以及这些观点：

_fields.html.erb：

<%= render 'shared/error_messages',:object => f.object %>
<fieldset>
<div class="left">
    <%= f.label :first_name %><br/>
    <%= f.text_field :first_name %>
</div>
<div>
    <%= f.label :last_name %><br/>
    <%= f.text_field :last_name %>
</div>
<div>
    <%= f.label :email %><br/>
    <%= f.text_field :email %>
</div>
<div>
    <%= f.label :organisation_id %><br/>
    <%= f.select(:organisation_id,current_user.organisation_names,{:include_blank => "--- None ---"},:id => 'organisation_select') %>
</div>
</fieldset>

<%= f.fields_for :address do |address| %>
  <%= render 'shared/address',:f => address %>
<% end %>

_address.html.erb：

<fieldset id="address_fields">
<div>
    <%= f.label :line1 %>
    <%= f.text_field :line1 %>
</div>
<div>
    <%= f.label :line2 %>
    <%= f.text_field :line2 %>
</div>
<div>
    <%= f.label :zip %>
    <%= f.text_field :zip %>
</div>  
<div>
    <%= f.label :city %>
    <%= f.text_field :city %>
</div>  
</fieldset>

people_controller.rb：

def new
  puts params.inspect
  @person = Person.new(:organisation_id => params[:organisation_id])
  @person.build_address
  @title = "New person"
end

{"action"=>"new","controller"=>"people"}

def edit
  puts params.inspect
  @title = @person.name
end

{"action"=>"edit","id"=>"69","controller"=>"people"}

def create
  puts params.inspect
  if params[:organisation_id]
    @person = current_user.organisations.build_person(params[:person])
  else
    @person = current_user.people.build(params[:person])
  end
  if @person.save
    flash[:success] = "Person created."
    redirect_to people_path
  else
    render :action => "new"
  end
end

{"commit"=>"Create","action"=>"create","person"=>{"last_name"=>"Doe","organisation_id"=>"9","email"=>"john.doe@email.com","first_name"=>"John","address_attributes"=>{"city"=>"Chicago","zip"=>"12345","line2"=>"Apt 1","line1"=>"1 Main Street"}},"authenticity_token"=>"Jp3XVLbA3X1SOigPezYFfEol0FGjcMHRTy6jQeM1OuI=","controller"=>"people","utf8"=>"✓"}

在我的Person模型中,我需要确保只有当一个人的organisation_id为空时,该人的地址字段必须存在.

我试过这样的事情：

validates :address,:presence => true,:if => "organisation_id.blank?"

但它不起作用.

如何才能做到这一点？

谢谢你的帮助.