Question

试图建立一个多态关联，注释可以属于其中，例如“照片”和“用户”。将对用户的评论视为“直接消息”。但是我把用户关联弄得一团糟。

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

class Photo < ActiveRecord::Base
  has_many :comments, as: :commentable, dependent: :destroy
end

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

这是不正确的。理想情况下，user.comments应该检索所有user_id == user.id的注释记录，而类似的user.messages应该检索类型为User并且它们是主题的所有Comment记录。

Answer 1

关系：

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

class Photo < ActiveRecord::Base
  has_many :comments, as: :commentable, dependent: :destroy
end

class User < ActiveRecord::Base
  has_many :comments, dependent: :destroy
  has_many :messages, as: :commentable, class_name: 'Comment'
end

模式：

# Comments
 ...
 t.integer :user_id
 t.integer :commentable_id
 t.string :commentable_type
 ...

然后您可以调用：

@user.comments # Get all comments created by particular user
@user.messages # Get all comments where particular user is a subject

Answer 2

您是否已将外键和类型列添加到comments表中？在迁移文件中：

  def change
    add_column :comments, :commentable_type, :integer
    add_column, :commentable_type, :string
    add_index :comments, [:commentable_type, :commentable_id]
  end

还要确保您拥有一个Message模型并具有关联性

class Message < ActiveRecord::Base
  has_many :comments, dependent: :destroy
  belongs_to :commentable, polymorphic: true
end

Rails多态注释关联

2 个答案: