Rails：ItemsController#show 中的 NoMethodError

Question

从我的ItemsController 访问@favorites = current_viewer.favorites_items.where(item_id: @item.id) 时收到错误消息：

NoMethodError in ItemsController#show 
undefined method `favorites_items' for nil:NilClass

items_controller.rb

 def show
   @favorites = current_viewer.favorites_items.where(item_id: @item.id)
   @comments = Comment.where(item_id: @item).order("created_at DESC")
   @items = Item.find(params[:id])
 end

模型关联：

class Viewer < ApplicationRecord
  devise :database_authenticatable, :registerable,
     :recoverable, :rememberable, :trackable, :validatable

  has_many :comments, dependent: :destroy
  has_many :favorites
 has_many :favorite_items, through: :favorites, source: :favorited, source_type: 'Item'

end

class Favorite < ApplicationRecord
  belongs_to :viewer
  belongs_to :favorited, polymorphic: true
end

class Item < ApplicationRecord
  belongs_to :seller
  belongs_to :category
  has_many :comments, dependent: :destroy

  mount_uploaders :attachments, ImageUploader
end

routes.rb

devise_for :viewers, controllers: {registrations: 'viewers/registrations', sessions: 'viewers/sessions'}
  devise_scope :viewer do
    get "viewers/index"=> "viewers/sessions#index", :as => "viewer_index"
  end

get '/favorites', to: 'favorite_items#index', as: 'favorites'
resources :favorite_items, only: [:create, :destroy]

更新 1

接下来我用 byebug 输入了三遍：

40: 
41:   # GET /items/1
42:   # GET /items/1.json
43:   def show
44:     byebug
=> 45:     @favorites = current_viewer.favorites_items.where(item_id: @item.id)
46:     @comments = Comment.where(item_id: @item).order("created_at DESC")
(byebug)

in /.rvm/gems/ruby-2.4.0/gems/actionpack-5.1.4/lib/action_controller/metal/rescue.rb
17: 
18:     private
19:       def process_action(*args)
20:         super
21:       rescue Exception => exception
=> 22:         request.env["action_dispatch.show_detailed_exceptions"] ||= show_detailed_exceptions?
23:         rescue_with_handler(exception) || raise
24:       end
25:   end
26: end
(byebug) 

18:     private
19:       def process_action(*args)
20:         super
21:       rescue Exception => exception
22:         request.env["action_dispatch.show_detailed_exceptions"] ||= show_detailed_exceptions?
=> 23:         rescue_with_handler(exception) || raise
24:       end
25:   end
26: end
(byebug) 

Answer 1

由于您有不同类型的用户角色，您需要像这样正确访问您的助手：

def show
   if current_viewer
    @favorites = current_viewer.favorites_items.where(item_id: @item.id)
   elsif
    @favorites = current_seller.favorites_items.where(item_id: @item.id)
   end
   @comments = Comment.where(item_id: @item).order("created_at DESC")
   @items = Item.find(params[:id])
 end

current_viewer 助手为 nil，因为您是作为卖家登录的！

Answer 2

您可能必须在过滤器之前设置以验证查看器

class ItemsController < ActionController::Base
  before_action :authenticate_viewer!

  def show
   ...
  end
end