在Rails 5.2中，无法访问多态关联中的某些路由

# routes.rb

resources :posts do
  resources :comments, only: [:index, :new, :create]
end

resources :articles do
  resources :comments, only: [:index, :new, :create]
end

# comments_controller.rb

class CommentsController < ApplicationController
  before_action :set_commentable

  def index
    @comments = @commentable.comments
  end

  def new
    @comment = @commentable.comments.new
  end

  def create
    @comment = @commentable.comments.new(comment_params)
    if @comment.save
      redirect_to @commentable, notice: 'Comment was successfully created.'
    else
      render :new
    end
  end

  private

  def set_commentable
    if params[:post_id]
      @commentable = Post.find(params[:post_id])
    elsif params[:article_id]
      @commentable = Article.find(params[:article_id])
    end
  end

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

<!-- comments/index.html.erb -->

<% @comments.each do |comment| %>
  <p><%= comment.content %></p>
<% end %>

<%= link_to 'New Comment', new_polymorphic_path([@commentable, :comment]) %>