<%= <a href="/page_title" class="user-mention" title="@page_title"><i>@</i>page_title</a> ? "#{t('site.name')} - #{<a href="/page_title.to_s" class="user-mention" title="@page_title.to_s"><i>@</i>page_title.to_s</a>}" : t('site.name') %>

试试 content_for

http://guides.rubyonrails.org/layouts_and_rendering.html#using-the-content_for-method

toturial 上是这样的 application.html.erb

<%=yield :title%>

然后具体页 <%provide(:title,"your title")%>

谢谢大家的建议我用 content_for 实现了，http://www.appfp.com