title: How to scope validation to specific model in polymorphic association.?
body: <p>I have two model <code>User</code> and <code>Investment</code> and one polymorhic model <code>Address</code></p>
  
  <pre><code>class User &lt; ActiveRecord::Base
      has_one :address, as: :addressable, dependent: :destroy
      accepts_nested_attributes_for :address
  end
  
  class Investment &lt; ActiveRecord::Base
      has_many :addresses, as: :addressable, dependent: :destroy
      accepts_nested_attributes_for :addresses, reject_if: lambda { |v| v['address'].blank? } &amp;&amp; :address_blank, :allow_destroy =&gt; true
  end
  
  
  class Address &lt; ActiveRecord::Base
     belongs_to :addressable, polymorphic: true
     validates :address, presence: true
  end
  </code></pre>
  
  <p>now <code>validates :address, presence: true</code> will applicable to both <code>Investment</code> as well as <code>User</code>
  but i want it to applicable to only <code>Investment</code> not to <code>User</code>. so how do i do that.</p>
  
  <p>Thanks.</p>