在Rails中通过嵌套语法构建对象时如何访问父对象

<%= form_for @post do |f| %>
  <%= f.label :title %>
  <%= f.text_field :title %>

  <%= f.fields_for :comments do |c| %>
    <%= c.label :content %>
    <%= c.text_area :content %>

    <%= c.hidden_field :post_id, value: @post.id %>
  <% end %>

  <%= f.submit %>
<% end %>

class CommentsController < ApplicationController
  def create
    @post = Post.find(params[:post_id])
    @comment = @post.comments.build(comment_params)
    # 对嵌套评论对象进行其他操作

    if @comment.save
      redirect_to @post
    else
      render 'new'
    end
  end

  private

  def comment_params
    params.require(:comment).permit(:content)
  end
end