Ruby on rails Rails 4:in-fields的字段

我正在学习RoR，并试图找到如何在另一个has_one模型中设置字段，如下所示：

class Child < ActiveRecord::Base
    belongs_to :father
    accepts_nested_attributes_for :father
end

class Father < ActiveRecord::Base
    has_one :child
    belongs_to :grandfather
    accepts_nested_attributes_for :grandfather
end


class Grandfather < ActiveRecord::Base
    has_one :father
end

我的表格：

<%= form_for(@child) do |f| %>
  <div class="field">
    <%= f.label :name %><br>
    <%= f.text_field :name %>
  </div>
  mother:<br>
  <%= f.fields_for :father do |ff| %>
    <%= ff.label :name %>
    <%= ff.text_field :name %><br>
      grand mother:<br>
      <%= f.fields_for :grandfather do |fff| %>
        <%= fff.label :name %>
        <%= fff.text_field :name %>
      <% end %>
  <% end %>
  <div class="actions">
    <%= f.submit %>
  </div>
<% end %>

母亲：



祖母：

我正在尝试检索以下数据：

<%= child.father.name %>
<%= child.father.grandfather.name %>

但是祖父的名字不起作用。 我找不到错误…有人可以帮忙吗？ 谢谢

尝试切换：

<%= f.fields_for :grandfather do |fff| %>

params.require(:child).permit(:name, father_attributes:[:name], grandfather_attributes:[:name])

致：

<%= ff.fields_for :grandfather do |fff| %>

params.require(:child).permit(:name, father_attributes:[:name], grandfather_attributes:[:name])

params.require(:child).permit(:name, father_attributes:[:name, grandfather_attributes:[:name]])