when delete co-author relation, the co-author will be reset nil

app/controllers/desktop/co_author_relations_controller.rb

@@ -27,6 +27,7 @@ class Desktop::CoAuthorRelationsController < ApplicationController
   def destroy
     @co_author_relation = CoAuthorRelation.find(params[:id])
     @co_author_relation.destroy
+    #reset_co_author_relation @co_author_relation
 
     render :json => {success: true, msg: "deleted successfully!"}
   end

app/helpers/desktop/co_author_relations_helper.rb

@@ -1,2 +1,8 @@
 module Desktop::CoAuthorRelationsHelper
+  def reset_co_author_relation relation
+    co_author = CoAuthor.where(co_author_relations_id: relation)
+    co_author.map do |c|
+      co_author.update_attributes(co_author_relations_id: nil)
+    end
+  end
 end

db/seeds.rb

@@ -33,7 +33,7 @@ FactoryGirl.define do
       { zh_tw: "#{name_tw[n]}",
         en: "#{name_en[n]}" }
     end
-    f.sequence(:type) do |n| "#{type[n%5]}" end
+    f.sequence(:co_author_relations_id) do |n| "#{CoAuthorRelation.all[n%type.size].id}" end
     f.sequence(:email) do |n| "#{email[n]}" end
     f.name_id BSON::ObjectId('4f45f3b9e9d02c5db9000067') #user_id, this is Chris' account
   end