关于ROR ONE_TO_ONE时，嵌套表单显示不出来的问题

In your code: <% f.fields_for :profile do |profile_form| %> Doesn't that need to be written like this (due to Rails 3 new behavior): <%= f.fields_for :profile do |profile_form| %>

当one to one 类型的表关系，想通过nested关系嵌套form实现，在form这个级别里，记得fields_for前面要加=才好用。

而如果是下一级，也就是form里面的one to many的fields_for里面再嵌套一级one to none，则不需要等号=。