如何在使用 friendly_id 时 find_by_id （对于多态关系）

Question

How do I allow find_by_id to work so my comments will work with my posts that have slugs via friendly_id? Is there an alternative approach to doing this?

我已经安装了一个名为 friendly_id 的 Ruby gem 并使用它在我的博文中创建了 slugs。这些博文通过 polymorphic 关系获得评论。我有这些相互冲突的方法，我认为是我的评论不起作用并引发错误的原因：

undefined method 'comments' for nil:NilClass

指向创建方法中的@comment = @commentable.comments.new comment_params评论控制器。

在我的评论模型中：

class Comment < ApplicationRecord
  belongs_to :commentable, polymorphic: true
  has_many :comments, as: :commentable, dependent: :destroy
end

在我的评论控制器中：

class CommentsController < ApplicationController
  before_action :find_commentable

  def new
    @comment = Comment.new
  end

  def create
    @comment = @commentable.comments.new comment_params
    if @comment.save
      flash[:success] = "Thanks for sharing your thoughts!"
      redirect_back fallback_location: root_path
    else
      flash[:danger] = "There was an error posting your comment!"
      redirect_back fallback_location: root_path
    end
  end

  private

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

  def find_commentable
    @commentable = Comment.find_by_id(params[:comment_id]) if params[:comment_id]
    @commentable = Post.find_by_id(params[:post_id]) if params[:post_id]
  end
end

在我的Post模型中：has_many :comments, as: :commentable

我的路线：

resources :comments do
  resources :comments
end

我的服务器日志：

app/controllers/comments_controller.rb:9:in `create'
Started POST "/posts/top-5-audio-industry-blogs/comments" for 127.0.0.1 at 2018-06-30 10:35:09 -0300
Processing by CommentsController#create as HTML
Parameters: {"utf8"=>"✓", "authenticity_token"=>"[token]", "comment"=>{"body"=>"Hey, thanks for checking out the article! Any questions? Just ask me here and I'll be happy to help.", "name"=>"name", "email"=>"email", "nickname"=>""}, "commit"=>"Post Comment", "post_id"=>"top-5-audio-industry-blogs"}
Post Load (0.0ms)  SELECT  "posts".* FROM "posts" WHERE "posts"."id" =  ORDER BY "posts"."created_at" DESC LIMIT   [["id", 0], ["LIMIT", 1]]
Completed 500 Internal Server Error in 27ms (ActiveRecord: 6.0ms)



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

这是我唯一能想到的导致此错误的原因，因为它没有任何问题。提前感谢您的帮助！

Answer 1

根据 docs，您需要查询 Comment 和 Post 模型，因为帖子有 slugs 而评论没有。见下文：

def find_commentable
  @commentable = if params[:comment_id]
                   Comment.find_by_id(params[:comment_id])
                 elsif params[:post_id]
                   Post.friendly.find(params[:post_id])
                 end

  # You should also handle the case if `@commentable` is `nil` after above.
  redirect_to somewhere, error: 'Post/Comment not found' unless @commentable
end

如何在使用 friendly_id 时 find_by_id （对于多态关系）

How to find_by_id when using friendly_id (for polymorphic relations)

ruby

ruby-on-rails

slug

friendly-id