我的一个字段总保存不到数据库中，给看一下

def create
   count = Teacher.count
   if count == 0 #第一个注册者拥有最高权限3，自动为管理员
      params[:teacher][:power] = 3
   else
      params[:teacher][:power] = 0 #其他的拥有最低权限0，等待管理员管理权限
   end
   
   @teacher = Teacher.new(params[:teacher])
   
   if @teacher.save
     flash[:notice] = "Teacher was successfully created"
     redirect_to :action => :login
   else
     redirect_to :action => :new
   end
 end 

  <%= error_messages_for 'teacher' %>

  <table>
   <tr> 
      <td><label for="teacher_name">姓名:</label></td>
      <td><%= text_field 'teacher','name'%></td>
   </tr>
   <tr>
     <td> <label for="teacher_display_name">昵称：</label></td>
     <td><%= text_field 'teacher','display_name' %></td>
   </tr>
   <tr>
     <td> <label for="teacher_password">密码：</label></td>
     <td><%= password_field 'teacher','password' %></td>
   </tr>
   <tr>
     <td> <label for="teacher_password_confirmation">再次输入密码：</label></td>
     <td><%= password_field 'teacher','password_confirmation' %></td>
   </tr>
        <%= hidden_field 'teacher','power'%>
 </table>

  create_table "teachers", :force => true do |t|
    t.column "name",         :string
    t.column "display_name", :string
    t.column "password",     :string
    t.column "power",        :integer
  end

@teacher = Teacher.new(params[:teacher])  
teacher.power = 3 if Teacher.count == 0

@teacher = Teacher.new(params[:teacher])  
teacher.power = 3 if Teacher.count == 0

 def init_power
    if Teacher.count == 0
       self.power = 3
    else
      self.power = 0
    end
  end

def create
   @teacher = Teacher.new(params[:teacher])
   @teacher.init_power

   if @teacher.save
     flash[:notice] = "Teacher was successfully created"
     redirect_to :action => :login
   else
     redirect_to :action => :new
   end
 end

@teacher = Teacher.new(params[:teacher])
if Teacher.count==0 then
  @teacher.power = 3
else
  @teacher.power = 0
end