prevent multiple subscriptions to same channel on same page

lib/private_pub/view_helpers.rb

@@ -15,7 +15,11 @@ def publish_to(channel, data = nil, &block)
     def subscribe_to(channel)
       subscription = PrivatePub.subscription(:channel => channel)
       content_tag "script", :type => "text/javascript" do
-        raw("PrivatePub.sign(#{subscription.to_json});")
+        raw ("
+          if(PrivatePub.subscriptions['#{channel}'] === undefined){
+            PrivatePub.sign(#{subscription.to_json});
+          }
+        ")
       end
     end
   end