问当使用关联时，Rails嵌套属性的复数？

EN

 <% if @article.photos.exists? %>
     <div class="row thumbnailrow">
       <% @article.photos.each do |x| %>
         <div class="col-xs-3">
           <!--<img src="http://placehold.it/300x150" class="img-responsive"/>-->
           <%= image_tag x.image.url(:full), :class=> "img-responsive" %>
         </div>
       <% end %>
     </div>
 <% end %> 

class Article < ActiveRecord::Base

belongs_to :user

validates_presence_of :title,length: {minimum: 20, maximum:100}, :message =>" Enter a valid title. Minimum of 20 characters"
validates_presence_of :category, presence: true
#validates_presence_of :content, presence: true, length: {minimum: 500, maximum: 1000}
validates_associated :photos, :message => "Please use a valid image"
has_many :photos, dependent: :destroy

accepts_nested_attributes_for :photos, reject_if: proc { |attributes| attributes['image'].blank?} 

def author
    if user.present?
        [user.first_name, user.last_name].reject(&:blank?).join(' ')
    else
        "author name"
    end
end
end

class Photo < ActiveRecord::Base
has_attached_file :image, :styles => { :full => "640x480#", :medium => "300x300>",     :thumb => "100x100>" }, :default_url => "http://placehold.it/350x200"
validates_attachment_content_type :image, :content_type => /\Aimage\/.*\Z/

validates :image, :attachment_presence => true


belongs_to :article

end