Atom

controller

####Conroller
ActiveAdmin.register Post do
    controller do
      def feed
        @posts = Post.all(:select => "title, created_at",  :limit => 20) 
          respond_to do |format|
          format.html
          format.rss { render :layout => false } #index.rss.builder
        end
end
    end

  	index do
		column :title
		column :description, :sortable => false do |t|
			truncate(t.description, :length => 300)
		end
	    column "Created" , :created_at
	    default_actions
	end

	form :html => { :multipart => true } do |f|
		f.inputs :new_post  do
    	f.input :title
      f.input :description
      f.input :photo, :as => :file
      f.input :content, as: :html_editor
    end
    f.buttons
	end
   
    show do |ad|
      attributes_table do
		row :title
		row :description    
        row :image do
         link_to image_tag(ad.photo.url(:small)), ad.photo.url(:norm)
        end
      end
      active_admin_comments
    end
end
#######################################
index.atom.builder
atom_feed do |feed|
  feed.title "Fitu News"
  @posts.each do |post|
    feed.entry post do |entry|
      entry.title post.title
      entry.description post.description
    end
  end
end
########################################
index.rss.builder
xml.instruct! :xml, version: "1.0"
xml.rss version: "2.0" do
xml.channel do
xml.title "Fitu News"
xml.description "From BSUIR"
xml.link posts_url
@posts.each do |post|
xml.item do
xml.title post.title
xml.description post.description
xml.link post_url(post)
xml.guid post_url(post)
end
end
end
end
 #################