Question

我有一个国家偏好的应用。用户将有两种类型的国家偏好 - 事件和研究。将来可能会有更多。我更倾向于使用2个表来表示使用STI。我在执行此操作时优雅地配置Rails有点麻烦。我可以破解它，但我宁愿通过Rails惯例来做到这一点。我想要的是这样的：

class User < ActiveRecord::Base
  has_many event_countries, :through => :event_countries, :class_name => 'Country'
  has_many research_countries, :through => :research_countries, :class_name => 'Country'
end

class EventCountry < ActiveRecord::Base
  belongs_to :country
  belongs_to :user
end

class ResearchCountry < ActiveRecord::Base
  belongs_to :country
  belongs_to :user
end

class Country < ActiveRecord::Base
...
end

但这不起作用。鉴于这个“伪代码”有没有人知道如何在Rails中实际实现它？

Answer 1

我认为你要宣布他们错了，因为这应该正常工作。这就是:through指令的用途：

class User < ActiveRecord::Base
  has_many :event_countries
  has_many :countries_with_events,
    :through => :event_countries,
    :source => :country

  has_many :research_countries
  has_many :countries_with_researches,
    :through => :research_countries,
    :source => :country
end

class EventCountry < ActiveRecord::Base
  belongs_to :country
  belongs_to :user
end

class ResearchCountry < ActiveRecord::Base
  belongs_to :country
  belongs_to :user
end

class Country < ActiveRecord::Base
  # ...
end

许多尴尬来自你为桌子选择的标签。虽然乍一看它们看似合理，但你使用它们的方式最终会使它们变得困难。

您可能希望将research_countries称为user_research_countries，以便关系名称可以user.research_countries作为:through：

class User < ActiveRecord::Base
  has_many :user_event_countries
  has_many :event_countries,
    :through => :user_event_countries,
    :source => :country

  has_many :user_research_countries
  has_many :research_countries,
    :through => :user_research_countries,
    :source => :country
end

class UserEventCountry < ActiveRecord::Base
  belongs_to :country
  belongs_to :user
end

class UserResearchCountry < ActiveRecord::Base
  belongs_to :country
  belongs_to :user
end

class Country < ActiveRecord::Base
  # ...
end

您可以通过向用户国家/地区关联表添加一个字段来进一步重构，其中包含一个或多个标记，在这种情况下将是研究或事件或以后需要的任何标记：

class User < ActiveRecord::Base
  has_many :user_countries
  has_many :event_countries,
    :through => :user_countries,
    :source => :country,
    :conditions => { :event => true }
  has_many :research_countries,
    :through => :user_countries,
    :source => :country,
    :conditions => { :research => true }
end

class UserCountry < ActiveRecord::Base
  belongs_to :country
  belongs_to :user

  # * column :event, :boolean
  # * column :research, :boolean
end

class Country < ActiveRecord::Base
  # ...
end

如何在Rails中两次加入相同的2个模型？

1 个答案: