非支架生成的情况下，验证错误信息输出方法，<%= f.error_messages %>错误

rails3下，<%= f.error_messages %>替换为

<%if@post.errors.any?%>

<div id="error_explanation">

<h2><%= pluralize(@post.errors.count,"error")%> prohibited this post from being saved:</h2>

<ul>

<%@post.errors.full_messages.each do|msg|%>

<li><%= msg %></li>

<%end%>

</ul>

</div>

<%end%>