如何在 Rails 5 中模拟“has_many”关联的“OR”条件？答案

【问题标题】：How can I simulate `OR` conditions for `has_many` association in Rails 5?如何在 Rails 5 中模拟“has_many”关联的“OR”条件？
【发布时间】：2017-03-15 17:59:36
【问题描述】：

我想模拟has_many 关联的OR 条件，这样我就不会丢失活动记录关联。我知道这可以使用scope 或实例方法来实现，但在这种情况下，我将失去关联。

class Game < ActiveRecord::Base
  belongs_to :home_team, :class_name => "Team"
  belongs_to :away_team, :class_name => "Team"
  has_many :sponsors
end
class Sponsor < ActiveReord::Base
  belongs_to :game
end
class Team < ActiveRecord::Base
  has_many :away_games, :class_name => "Game", :foreign_key => "away_team_id"
  has_many :home_games, :class_name => "Game", :foreign_key => "home_team_id"

  # what I want here like:
  # has_many :games, :foreign_key => [:home_team_id, :away_team_id] 
  # so I could achieve without losing association helper:
  # has_many :sponsors through: :games
end

【问题讨论】：

标签： ruby-on-rails rails-activerecord ruby-on-rails-5

【解决方案1】：

你可以这样做：

这里会先删除原来的作用域:team_id，改用away_team_id或home_team_id。

has_many :games, ->(team){ unscope(where: :team_id)
          .where('away_team_id = :team_id OR home_team_id = :team_id', team_id: team.id) }

has_many :sponsors, through: :games

【讨论】：