删除多态关联
Deleting polymorphic associations
我通过关注 this great article.
为我的 rails 应用实施了一个收藏系统
这是我的设置：
favorite.rb
class Favorite < ActiveRecord::Base
belongs_to :user
belongs_to :favorited, polymorphic: true
end
project.rb
class Project < ActiveRecord::Base
belongs_to :user
has_many :favorites, as: :favorited
has_many :fans, through: :favorites, source: :user
user.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
问题来了。
我有一些最喜欢的项目。
我使用 Project.delete_all 删除了我的项目，而某些项目仍然 "favorited" 但现在我收到错误消息：
ActionView::Template::Error (undefined method `favorite_projects' for nil:NilClass):
我敢肯定，如果我在删除之前 "unfavorited" 所有这些项目，就不会出现此错误。
有人知道如何解决这个问题吗？
根据 Rails API docs on delete_all:
Deletes the records matching conditions without instantiating the records first, and hence not calling the destroy method nor invoking callbacks. This is a single SQL DELETE statement that goes straight to the database, much more efficient than destroy_all. Be careful with relations though, in particular :dependent rules defined on associations are not honored. Returns the number of rows affected.
我把相关文字加粗了；并进一步在文档中：
If you need to destroy dependent associations or call your before_* or after_destroy callbacks, use the destroy_all method instead.
总而言之，您现在有孤立的 Favorite 条记录。我会启动 rails c 并销毁孤立的记录，下次你 运行 任何 delete 功能时要小心。
您需要设置依赖选项。
has_many :favorites, as: :favorited, dependent: :destroy
在将对象留在数据库中没有意义的任何关联上设置此项。
您不需要在 through has_many 关联上设置它。
我通过关注 this great article.
为我的 rails 应用实施了一个收藏系统这是我的设置：
favorite.rb
class Favorite < ActiveRecord::Base
belongs_to :user
belongs_to :favorited, polymorphic: true
end
project.rb
class Project < ActiveRecord::Base
belongs_to :user
has_many :favorites, as: :favorited
has_many :fans, through: :favorites, source: :user
user.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
问题来了。
我有一些最喜欢的项目。
我使用 Project.delete_all 删除了我的项目，而某些项目仍然 "favorited" 但现在我收到错误消息：
ActionView::Template::Error (undefined method `favorite_projects' for nil:NilClass):
我敢肯定，如果我在删除之前 "unfavorited" 所有这些项目，就不会出现此错误。
有人知道如何解决这个问题吗？
根据 Rails API docs on delete_all:
Deletes the records matching conditions without instantiating the records first, and hence not calling the destroy method nor invoking callbacks. This is a single SQL DELETE statement that goes straight to the database, much more efficient than destroy_all. Be careful with relations though, in particular :dependent rules defined on associations are not honored. Returns the number of rows affected.
我把相关文字加粗了；并进一步在文档中：
If you need to destroy dependent associations or call your before_* or after_destroy callbacks, use the destroy_all method instead.
总而言之，您现在有孤立的 Favorite 条记录。我会启动 rails c 并销毁孤立的记录，下次你 运行 任何 delete 功能时要小心。
您需要设置依赖选项。
has_many :favorites, as: :favorited, dependent: :destroy
在将对象留在数据库中没有意义的任何关联上设置此项。
您不需要在 through has_many 关联上设置它。