user model save bug

app/models/user.rb

@@ -86,8 +86,6 @@ class User < Principal
 ## added by xianbo for delete 
   has_many :biding_projects, :dependent => :destroy
   has_many :contesting_projects, :dependent => :destroy
-  has_many :contesting_softapplications, :dependent => :destroy
-  has_many :projecting_softapplications, :dependent => :destroy
   belongs_to :softapplication, :foreign_key => 'id', :dependent => :destroy
 ##ended by xianbo
   
@@ -203,14 +201,14 @@ class User < Principal
   # ======================================================================
   # 集中处理 User 扩展表为空的问题
   validate :valid_user_extensions
-  before_save :save_user_extensions
+  after_save :save_user_extensions
 
   def extensions
-    self.user_extensions ||= self.create_user_extensions
+    self.user_extensions ||= UserExtensions.new
   end
 
   def respond_to?(m, include_private = false)
-    flag = extensions.respond_to? m.to_sym
+    flag = UserExtensions.instance_methods.include? m.to_sym
     if flag
       flag
     else