Rails 4 - 多态关联 - 多个关联(Rails 4 - Polymorphic associations - multiple associations)

 我正在尝试制作Rails 4应用程序。 
 
 我有一个多态的评论模型。 我也有用户，个人资料和文章的模型。 
 
 协会是： 
 
 article.rb 
 
belongs_to :user
has_many :comments, as: :commentable
accepts_nested_attributes_for :comments
 
 comments.rb 
 
belongs_to :user
belongs_to :commentable, :polymorphic => true
 
 profile.rb 
 
belongs_to :user
has_many :addresses, as: :addressable
 
 user.rb 
 
has_many :articles
has_many :comments
has_one :profile
 
 我很难理解这在实践中是如何运作的。 
 
 当我使用我的控制台创建注释时，如下所示： 
 
 
 
 Comment.create（可评论：Article.first，user_id：“1”，意见：“test”）文章加载（15.5ms）SELECT“articles”。* FROM“articles”ORDER BY“articles”。“created_at”DESC LIMIT 1 （0.2ms）BEGIN SQL（6.3ms）INSERT INTO“comments”（“commentable_id”，“commentable_type”，“user_id”，“views”，“created_at”，“updated_at”）VALUES（$ 1，$ 2，$ 3，$ 4， $ 5，$ 6）RETURNING“id”[[“commentable_id”，3]，[“commentable_type”，“Article”]，[“user_id”，1]，[“opinion”，“test”]，[“created_at”， “2016-01-01 01：51：20.711415”]，[“updated_at”，“2016-01-01 01：51：20.711415”]]（1.3ms）COMMIT =>＃ 
 
 
 这样可行。 
 
 但是，当我转到视图并尝试使用表单创建新注释时，我得到： 
 
SELECT  "articles".* FROM "articles" WHERE "articles"."id" = $1  ORDER BY "articles"."created_at" DESC LIMIT 1  [["id", 3]]
  User Load (0.3ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1  ORDER BY "users"."id" ASC LIMIT 1  [["id", 1]]
Unpermitted parameter: comment
   (0.2ms)  BEGIN
   (0.1ms)  COMMIT
[ActiveJob] Enqueued Searchkick::ReindexV2Job (Job ID: 4fd1ceb5-7882-4381-a2df-5913082af621) to Inline(searchkick) with arguments: "Article", "3"
 
 什么都没发生。 
 
 此外，我尝试按照本视频教程中的示例（大约7m：30s）： 
 
 https://gorails.com/episodes/comments-with-polymorphic-associations?autoplay=1 
 
 我更改了我的注释部分，它正在显示在控制台中创建的注释（但不在视图表单中）： 
 
<% @article.comments.each do | comment | %>
  <div class="well">
    <%= comment.opinion %>
    <div class="commentattribution">
      <%= comment.user.formal_name_and_title %>
    </div>
  </div>
<% end %>
 
 在我的文章显示页面中添加局部变量，我在其中呈现注释部分： 
 
<%= render 'comments/display', locals: {commentable: @article} %>
 
 并用@commentable替换开头行中的@article： 
 
<% @commentable.comments.each do | comment | %>
  <div class="well">
    <%= comment.opinion %>
    <div class="commentattribution">
      <%= comment.user.formal_name_and_title %>
    </div>
  </div>
<% end %>
 
 现在，当我保存并尝试渲染文章显示页面时，我收到此错误： 
 
undefined method `comments' for nil:NilClass
 
 我不明白这个错误信息意味着什么，但它一切正常，直到我试图引用值得赞扬而不是文章。 错误消息中引用的特定行项是： 
 
<% @commentable.comments.each do | comment | %>
 
 谁能看到这里出了什么问题？ 
 
 当我尝试： 
 
<% commentable.comments.each do | comment | %>
 
 我收到此错误： 
 
undefined local variable or method `commentable' for #<#<Class:0x007fd13b93dac8>:0x007fd134530270>
 
 我已经阅读了其他一些帖子，其中人们遇到了属于多个资源的多态关联问题。 例如，我的评论属于用户和文章。 我无法遵循该决议或正确掌握该安排的问题。 
 
 Joe Half Face的解决方案适用于评论表单，但现在唯一不起作用的部分是获取撰写文章的用户的名称以显示在页面上。 
 
 在我的文章展示页面中，我有： 
 
<div class="articletitle">
                    <%= @article.title %>
                </div>    
                <div class="commentattributionname">
                    <%= @article.user.try(:formal_name) %>
                </div>
                <div class="commentattributiontitle">
                    <%= @article.user.try(:formal_title) %>
                </div>
                <div class="commentattributiondate">
                    <%= @article.created_at.try(:strftime, '%e %B %Y') %>
                </div>
 
 标题，节目和创建日期显示，但不显示任何用户属性。 
 
 它只是代码检查器中显示的空白div容器。 

I am trying to make a Rails 4 app.
 
I have a comments model which is polymorphic. I also have models for user, profile and article.
 
The associations are:
 
article.rb
 
belongs_to :user
has_many :comments, as: :commentable
accepts_nested_attributes_for :comments
 
comments.rb
 
belongs_to :user
belongs_to :commentable, :polymorphic => true
 
profile.rb
 
belongs_to :user
has_many :addresses, as: :addressable
 
user.rb
 
has_many :articles
has_many :comments
has_one :profile
 
I'm struggling to understand how this works in practice. 
 
When I use my console to create a comment as follows:
 
 
 
Comment.create(commentable: Article.first, user_id: "1", opinion: "test") Article Load (15.5ms) SELECT "articles".* FROM "articles" ORDER BY "articles"."created_at" DESC LIMIT 1 (0.2ms) BEGIN SQL (6.3ms) INSERT INTO "comments" ("commentable_id", "commentable_type", "user_id", "opinion", "created_at", "updated_at") VALUES ($1, $2, $3, $4, $5, $6) RETURNING "id" [["commentable_id", 3], ["commentable_type", "Article"], ["user_id", 1], ["opinion", "test"], ["created_at", "2016-01-01 01:51:20.711415"], ["updated_at", "2016-01-01 01:51:20.711415"]] (1.3ms) COMMIT => #
 
 
That works.
 
However, when I go to the view and try to create a new comment using the form, I get:
 
SELECT  "articles".* FROM "articles" WHERE "articles"."id" = $1  ORDER BY "articles"."created_at" DESC LIMIT 1  [["id", 3]]
  User Load (0.3ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1  ORDER BY "users"."id" ASC LIMIT 1  [["id", 1]]
Unpermitted parameter: comment
   (0.2ms)  BEGIN
   (0.1ms)  COMMIT
[ActiveJob] Enqueued Searchkick::ReindexV2Job (Job ID: 4fd1ceb5-7882-4381-a2df-5913082af621) to Inline(searchkick) with arguments: "Article", "3"
 
Nothing happens.
 
Further, I tried following the example in this video tutorial (around 7m:30s):
 
https://gorails.com/episodes/comments-with-polymorphic-associations?autoplay=1
 
I changed my comments partial, which was working to display comments created in the console (but not in the view form) from:
 
<% @article.comments.each do | comment | %>
  <div class="well">
    <%= comment.opinion %>
    <div class="commentattribution">
      <%= comment.user.formal_name_and_title %>
    </div>
  </div>
<% end %>
 
to add a local variable in my articles show page where I render the comments partial:
 
<%= render 'comments/display', locals: {commentable: @article} %>
 
and replace @article in the opening line with @commentable:
 
<% @commentable.comments.each do | comment | %>
  <div class="well">
    <%= comment.opinion %>
    <div class="commentattribution">
      <%= comment.user.formal_name_and_title %>
    </div>
  </div>
<% end %>
 
Now, when I save that and try to render the article show page, I get this error:
 
undefined method `comments' for nil:NilClass
 
I don't understand what this error message means, but it was all working fine until I tried to reference commendable instead of article. The specific line item referenced in the error message is:
 
<% @commentable.comments.each do | comment | %>
 
Can anyone see what's going wrong here?
 
When I try:
 
<% commentable.comments.each do | comment | %>
 
I get this error:
 
undefined local variable or method `commentable' for #<#<Class:0x007fd13b93dac8>:0x007fd134530270>
 
I have read some other posts where people have had trouble with polymorphic associations belonging to more than one resource. For example, my comments belong to users as well as articles. I've not been able to follow the resolution or properly grasp the issue with that arrangement.
 
Joe Half Face's solution worked for the comments form, but the only part that isn't working now is getting the name of the user that wrote the article to appear on the page. 
 
In my articles show page, I have:
 
<div class="articletitle">
                    <%= @article.title %>
                </div>    
                <div class="commentattributionname">
                    <%= @article.user.try(:formal_name) %>
                </div>
                <div class="commentattributiontitle">
                    <%= @article.user.try(:formal_title) %>
                </div>
                <div class="commentattributiondate">
                    <%= @article.created_at.try(:strftime, '%e %B %Y') %>
                </div>
 
The title, shows and date created shows, but neither of the user attributes appear. 
 
It's just a blank div container showing in the code inspector.

原文：https://stackoverflow.com/questions/34553319