ruby-on-rails - 删除多态关联

Question

我已经按照 this great article 为我的 Rails 应用程序实现了收藏系统.

这是我的设置:

---

最喜欢的.rb

class Favorite < ActiveRecord::Base
  belongs_to :user
  belongs_to :favorited, polymorphic: true
end

---

项目.rb

class Project < ActiveRecord::Base
    belongs_to :user

    has_many :favorites, as: :favorited
    has_many :fans, through: :favorites, source: :user 

---

用户.rb

class User < ActiveRecord::Base
  has_many :listings
  has_many :projects
  has_many :favorites
  has_many :favorite_listings, through: :favorites, source: :favorited, source_type: 'Listing'
  has_many :favorite_projects, through: :favorites, source: :favorited, source_type: 'Project'

---

favorite_projects_controller.rb

class FavoriteProjectsController < ApplicationController
  before_action :set_project
  # before_action :correct_user
  # before_action :authenticate_user!

  def create
    if Favorite.create(favorited: @project, user: current_user)
      redirect_to @project, notice: 'Project has been favorited'
    else
      redirect_to @project, alert: 'Something went wrong...*sad panda*'
    end
  end

  def destroy
    Favorite.where(favorited_id: @project.id, user_id: current_user.id).first.destroy
    redirect_to @project, notice: 'Project is no longer in favorites'
  end

  private

  def set_project
    @project = Project.find(params[:project_id] || params[:id])
  end
end

---

问题就在这里。

我有一些最喜欢的项目。

我使用 Project.delete_all 删除了我的项目，而某些项目仍处于“收藏夹”状态，但现在出现错误:

 ActionView::Template::Error (undefined method `favorite_projects' for nil:NilClass):

我确信如果我在删除所有这些项目之前“取消收藏”它们，则不会出现此错误。

有人知道如何解决这个问题吗？

Answer 1

您需要设置依赖选项。

has_many :favorites, as: :favorited, dependent: :destroy

在任何将对象保留在数据库中没有意义的关联上设置此项。

您无需在 through has_many 关联上设置它。