Ruby on Rails:多态关联混淆

Question

我在GitHub上贡献了一个ruby on rails应用程序，在那里我遇到了以下场景：

我有以下模型，我想转换成多态的：

class Comment < ActiveRecord::Base
  belongs_to :team
  belongs_to :user
  belongs_to :application
  belongs_to :project
end

class Team < ActiveRecord::Base
  has_many :comments
end

class Project < ActiveRecord::Base
  has_many :comments, -> { order('created_at DESC') }, dependent: :destroy
end

class User < ActiveRecord::Base
end

class Application < Rails::Application
end

我做了以下更改，使其具有多态特性：

执行数据库更改以删除team_id、project_id、application_id和user_id，并将commentable_id和commentable_type添加到comments表中。

rails指南中所述的模型修改：

class Comment < ActiveRecord::Base
  belongs_to :commentable, polymorphic: true
end

class Team < ActiveRecord::Base
  has_many :comments, as: :commentable
end

class Project < ActiveRecord::Base
  has_many :comments, as: :commentable, -> { order('created_at DESC') }, dependent: :destroy
end

虽然我将它与默认作用域一起使用，但它不允许我与默认作用域一起使用，并给出了以下行的错误：

has_many :comments, as: :commentable, -> { order('created_at DESC') }, dependent: :destroy

我对以下模型的更改感到困惑：

class User < ActiveRecord::Base
end

class Application < ActiveRecord::Base
end

我是否需要在User和Application模型中进行以下更改？

class User < ActiveRecord::Base
  has_many :comments, as: :commentable
end

class Application < ActiveRecord::Base
  has_many :comments, as: :commentable
end

提前感谢！

Answer 1

如果您的用户/应用程序对象需要注释，则添加

class User < ActiveRecord::Base
  has_many :comments, as: :commentable
end

class Application < ActiveRecord::Base
  has_many :comments, as: :commentable
end

否则create belongs_to/has_many关系不是多态的，例如。

class User < ActiveRecord::Base
  has_many :comments
end

class Application < ActiveRecord::Base
  has_many :comments
end