怕看不懂，定义几个常量

app/models/user_extensions.rb

@@ -9,6 +9,10 @@
 class UserExtensions < ActiveRecord::Base
   belongs_to :user
   attr_accessible :user_id,:birthday,:brief_introduction,:gender,:location,:occupation,:work_experience,:zip_code,:identity, :technical_title,:student_id
+  TEACHER = 0
+  STUDENT = 1
+  ENTERPRISE = 2
+  DEVELOPER = 3
   #this method was used to update the table user_extensions
   def update_user_extensions(birthday=nil,brief_introduction=nil,
                               gender=nil,location=nil,occupation=nil,work_experience=nil,zip_code=nil)

app/views/layouts/_base_header.html.erb

@@ -12,7 +12,7 @@
 
 			<%=link_to_user(User.current)%>
 			<ul class="sub_menu">
-				<% if User.current.user_extensions && [0,1].include?(User.current.user_extensions.identity) -%>
+				<% if User.current.user_extensions && [UserExtensions::TEACHER, UserExtensions::STUDENT].include?(User.current.user_extensions.identity) -%>
 				<li><%=link_to l(:label_my_course), user_courses_user_path(User.current), target:'my_path' %></li>
 				<% end -%>
 				<li><%=link_to l(:label_my_projects), user_projects_user_path(User.current), target:'my_path' %></li>