Question

我有一个相当标准的商业模式，Account个实例可以互相关注。它就像Twitter一样。连接模型称为Relationship。

class Account
  has_many :active_relationships, class_name: 'Relationship', 
    dependent: :destroy, foreign_key: :follower_id
  has_many :passive_relationships, class_name: 'Relationship', 
    dependent: :destroy, foreign_key: :followed_id
  # These are accounts that a given account is following
  has_many :friends, through: :active_relationships, source: :followed
  # These are accounts that follow the given account
  has_many :followers, through: :passive_relationships, source: :follower
end

class Relationship
  belongs_to :follower, class_name: 'Account'
  belongs_to :followed, class_name: 'Account'
end

我想查看跟随两个或更多其他特定帐户的推特帐户。

例如，假设数据库中存在四个帐户。他们将艾伦，贝卡，查理和戴夫命名为。戴夫跟随艾伦和查理。贝卡只跟随艾伦。当我应用我的范围时，它应该只返回Dave。

我可以查看关注一个特定帐户的用户：

Account.includes(:active_relationships)
  .where(relationships: { followed_id: alan.id })

但链接where子句返回零的结果，因为DB查找关系记录，其中followed_id同时等于两个不同的帐户ID。这显然是不可能的。

Account.includes(:active_relationships)
  .where(relationships: { followed_id: alan.id })
  .where(relationships: { followed_id: charlie.id })

如何使用ActiveRecord正确实现此功能？

确定与其他两个特定模型相结合的记录

0 个答案: