Ruby on rails 多态注释：can'；t通行证类型和id（NoMethodError代表nil:NilClass）

我试图为

问题

和

答案

创建多态注释，但是当我点击“创建注释”表单上的“创建”按钮时，

可注释类型

和

可注释id

从未通过。我可以通过rails控制台成功地创建一个新的注释，但不能通过表单（目前我正在测试注释的问题）。我在控制器的

load\u commentable

或

create

中遇到错误，例如：

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

app/controllers/comments_controller.rb:9:in `create'

似乎

@commentable

是

nil

（因为它没有

commentable\u type

和

commentable\u id

参数？）。 我错过了什么

请注意：

class CreateComments < ActiveRecord::Migration[5.1]
  def change
    create_table :comments do |t|
      t.references :user, foreign_key: true
      t.text :body, null:false
      t.references :commentable, polymorphic: true, index: true

      t.timestamps
    end
      add_index :comments, [:commentable_id, :commentable_type]
  end
end

评论表单部分_comment_form.html.slim：

    h4 Add a comment
    .comment_errors
    = form_for [@commentable, Comment.new], remote: true do |f|
      .form-group
        = f.label :body, 'Comment'
        = f.text_area :body, class: 'form-control'
      p= f.submit 'Create', class: 'btn btn-primary'

财务主任评论：

class CommentsController < ApplicationController
  before_action :authenticate_user!
  before_action :load_commentable, only: [:create]

  def create
    @comment = @commentable.comments.create(comment_params.merge(user: current_user))
  end

  private

  def load_commentable
    if params[:comment][:commentable_type] == 'Answer'
      @commentable = Answer.find(params[:comment][:commentable_id])
      gon.answer_id = @commentable.id
    elsif params[:comment][:commentable_type] == 'Question'
      gon.answer_id = @commentable.id
      @commentable = Question.find(params[:comment][:commentable_id])
    end
  end

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

错误日志：

app/controllers/comments_controller.rb:7:in `create'
Started POST "/comments" for 10.0.2.2 at 2017-11-20 20:54:42 +0000
Cannot render console from 10.0.2.2! Allowed networks: 127.0.0.1, ::1, 127.0.0.0/127.255.255.255
Processing by CommentsController#create as JS
  Parameters: {"utf8"=>"✓", "comment"=>{"body"=>"kkkk"}, "commit"=>"Create"}
  User Load (0.4ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 ORDER BY "users"."id" ASC LIMIT $2  [["id", 41], ["LIMIT", 1]]
Completed 500 Internal Server Error in 3ms (ActiveRecord: 0.4ms)



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

app/controllers/comments_controller.rb:7:in `create'

---

我认为您的

partial\u comment\u form.html.slim

应该是这样的：

h4 Add a comment
.comment_errors
= form_for [@commentable, Comment.new], remote: true do |f|
  .form-group
    = f.label :body, 'Comment'
    = f.text_area :body, class: 'form-control'
    = hidden_field_tag 'commentable[id]', @commentable.id
    = hidden_field_tag 'commentable[type]', @commentable.class.name
  p= f.submit 'Create', class: 'btn btn-primary'

Parameters: {"utf8"=>"✓", "comment"=>{"body"=>"kkkk"}, "commentable"=>{"id"=>"1", "type"=>"Question"}, commit"=>"Create"}

def load_commentable
  @commentable = commentable_params[:type].constantize.find_by(id: commentable_params[:id])
  gon.answer_id = @commentable.id
end

def commentable_params
  param.require(:commentable).permit(:id, :type)
end

这将为您提供类似以下内容的参数：

h4 Add a comment
.comment_errors
= form_for [@commentable, Comment.new], remote: true do |f|
  .form-group
    = f.label :body, 'Comment'
    = f.text_area :body, class: 'form-control'
    = hidden_field_tag 'commentable[id]', @commentable.id
    = hidden_field_tag 'commentable[type]', @commentable.class.name
  p= f.submit 'Create', class: 'btn btn-primary'

Parameters: {"utf8"=>"✓", "comment"=>{"body"=>"kkkk"}, "commentable"=>{"id"=>"1", "type"=>"Question"}, commit"=>"Create"}

def load_commentable
  @commentable = commentable_params[:type].constantize.find_by(id: commentable_params[:id])
  gon.answer_id = @commentable.id
end

def commentable_params
  param.require(:commentable).permit(:id, :type)
end

然后，将

load\u commentable

更改为如下内容：

h4 Add a comment
.comment_errors
= form_for [@commentable, Comment.new], remote: true do |f|
  .form-group
    = f.label :body, 'Comment'
    = f.text_area :body, class: 'form-control'
    = hidden_field_tag 'commentable[id]', @commentable.id
    = hidden_field_tag 'commentable[type]', @commentable.class.name
  p= f.submit 'Create', class: 'btn btn-primary'

Parameters: {"utf8"=>"✓", "comment"=>{"body"=>"kkkk"}, "commentable"=>{"id"=>"1", "type"=>"Question"}, commit"=>"Create"}

def load_commentable
  @commentable = commentable_params[:type].constantize.find_by(id: commentable_params[:id])
  gon.answer_id = @commentable.id
end

def commentable_params
  param.require(:commentable).permit(:id, :type)
end

（顺便说一句，gon.当你有问题的时候，回答这个问题似乎很奇怪。但是，我不知道…）

当然，这需要类似于：

h4 Add a comment
.comment_errors
= form_for [@commentable, Comment.new], remote: true do |f|
  .form-group
    = f.label :body, 'Comment'
    = f.text_area :body, class: 'form-control'
    = hidden_field_tag 'commentable[id]', @commentable.id
    = hidden_field_tag 'commentable[type]', @commentable.class.name
  p= f.submit 'Create', class: 'btn btn-primary'

Parameters: {"utf8"=>"✓", "comment"=>{"body"=>"kkkk"}, "commentable"=>{"id"=>"1", "type"=>"Question"}, commit"=>"Create"}

def load_commentable
  @commentable = commentable_params[:type].constantize.find_by(id: commentable_params[:id])
  gon.answer_id = @commentable.id
end

def commentable_params
  param.require(:commentable).permit(:id, :type)
end

---

查看您的

参数

：

“comment”=>{“body”=>“kkkk”}

。看到少了什么吗？然后看看你的表格。你有

@commentable

，但是你在哪里向表单中添加它的值呢？id、用户id、commentable类型和commentable id参数都丢失了，但是我不明白为什么以及如何修复这个Google for

隐藏字段的问题。。。顺便说一句，我不知道id是指什么。但是我想你不需要
user\u id
，因为你可以通过designe使用它（我想类似于
current\u user.id
。但是，我不使用designe，所以这可能不完全正确）。id是注释的id。我以前尝试过隐藏字段，但这不起作用，并且出现了类似的错误，我还了解到更好的解决方案是在控制器中动态传递这些字段，但无法修复代码。