通过表单 [Rails 5] 提交嵌套资源时遇到问题

Question

我有一个Document，has_manySection，每个sectionhas_oneComment。我希望能够在 Document show 视图中同时创建 sections 和 comments，但是我无法让 comments 通过。

这是我得到的最接近的相关代码：

class CommentsController < ApplicationController
  def create
    @section = Section.find(params[:id])
    @section.comment.create(comment_params)
  end

  private

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

路由：

resources :documents, shallow: true do
  resources :sections do
    resources :comments
  end
end

以及具有以下形式的视图：

# app/views/documents/show.html.erb

<% @document.sections.each do |section| %>
  <%= section.body %>

  <% if section.comment %>
    <p>
      <%= section.comment %>
    </p>
  <% else %>
    <%= form_with url: section_comments_path(section.id), scope: 'comment' do |form| %>
      <%= form.text_field :body, placeholder: "Comment" %>
      <%= form.submit %>
    <% end %>
  <% end %>
<% end %>

这一切似乎都在为我检查，但是当我尝试 post 发表评论时，我得到的是：

Started POST "/sections/51/comments" for ::1 at 2019-05-24 23:29:06 +0000
Processing by CommentsController#create as JS
  Parameters: {"utf8"=>"✓", "authenticity_token"=>[...], "comment"=>{"body"=>"asdas"}, "commit"=>"Save comment", "section_id"=>"51"}
  Section Load (0.5ms)  SELECT  "sections".* FROM "sections" WHERE "sections"."id" = ? LIMIT ?  [["id", 51], ["LIMIT", 1]]
  comment Load (0.4ms)  SELECT  "comments".* FROM "comments" WHERE "comments"."section_id" = ? LIMIT ?  [["section_id", 51], ["LIMIT", 1]]
Completed 500 Internal Server Error in 11ms (ActiveRecord: 0.9ms)

NoMethodError (undefined method `create' for nil:NilClass):

app/controllers/comments_controller.rb:4:in `create'

有什么想法吗？

Answer 1

一个has_one关系returns对象本身。因此，@section.comment.create(comment_params) 将不起作用，因为 @section.comment 为零。相反，尝试类似...

def create
  @section = Section.find(params[:section_id])
  @comment = Comment.create(comment_params)
  @section.comment = @comment

  ...
end

或者，如 Rails 指南中所述...

When initializing a new has_one or belongs_to association you must use the build_ prefix to build the association, rather than the association.build method that would be used for has_many or has_and_belongs_to_many associations. To create one, use the create_ prefix.

看起来像这样

def create
  @section = Section.find(params[:section_id])
  @section.create_comment(comment_params)

  ...
end

Answer 2

您可能需要更改：

@section.comment.create(comment_params)

至：

@section.comments.create(comment_params)

如果还是不行，试试：

@section.comment.create!(comment_params)

看看异常是怎么说的

通过表单 [Rails 5] 提交嵌套资源时遇到问题

Having trouble submitting nested resource through form [Rails 5]

ruby-on-rails

forms

ruby-on-rails-5

nested-resources