可以问个新手问题吗-为什么不显示验证信息

我自己写了一个表单的修改验证，为什么验证信息不能提示呢？
我想要的效果

 

Form的代码

<%=form_tag({:action=>"region_save" , :id=>@region.id}) %>
<table class="datatable" width='90%'>
<tr bgcolor='#BFBFD2'><td colspan='2' style="valign:middle;"><h2>Region</h2></td></tr>
<tr><td>Region Name:</td><td><%= text_field("region","name") %></td></tr>
<tr bgcolor='#FFFCDF'><td>Region IP:</td><td><%= text_field("region","ip")%></td></tr>
<tr><td colspan='2'><%=submit_tag %></td></tr>
</table>
</form>

 

Controller的代码

  def region_save
    region_id=params[:id]
    region_name=params[:region][:name]
    region_ip=params[:region][:ip]
    if (region_id.nil?)
      region=Region.new()
    else
      region=Region.find(region_id)
    end
    region[:name]=region_name
    region[:ip]=region_ip
    region.save()
    redirect_to :action => "region_list"    
  end

  Model的代码

class Region < ActiveRecord::Base
  validates_uniqueness_of :name
  validates_uniqueness_of :ip
  validates_presence_of   :name,
                          :message=>"Please input a name to region."
  validates_format_of     :ip,
                          :with => /^(\d{1,2}|1\d\d|2[0-4]\d|25[0-5])\.(\d{1,2}|1\d\d|2[0-4]\d|25[0-5])\.(\d{1,2}|1\d\d|2[0-4]\d|25[0-5])\.(\d{1,2}|1\d\d|2[0-4]\d|25[0-5])$/,
                          :message=>"Please input a right format of ip address."
end