相关疑难解决方法(0)

Ruby和Rails都是新手,但我现在已经预订了教育(显然没什么意义,哈哈).

我有两个模型,Event和User通过表EventUser加入

class User < ActiveRecord::Base
  has_many :event_users
  has_many :events, :through => :event_users
end

class EventUser < ActiveRecord::Base
  belongs_to :event
  belongs_to :user

  #For clarity's sake, EventUser also has a boolean column "active", among others
end

class Event < ActiveRecord::Base
  has_many :event_users
  has_many :users, :through => :event_users
end

这个项目是一个日历,我必须跟踪人们注册并为特定事件划出他们的名字.我认为多对多是一个很好的方法,但我做不到这样的事情:

u = User.find :first
active_events = u.events.find_by_active(true)

因为事件实际上没有那些额外的数据,所以EventUser模型可以.虽然我能做到:

u = User.find :first
active_events = []
u.event_users.find_by_active(true).do |eu|
  active_events << eu.event
end

这似乎与"铁路方式"相反.任何人都可以启发我,今晚(今天早上)这已经困扰了我很长时间？

代码(Rails 4.0.0)

class Track < ActiveRecord::Base
  has_many :artist_tracks
  has_many :owning_artists,
              -> { where(:artist_tracks => { :artistic_role_id => 1 }) },
              :through => :artist_tracks,
              :source => :artist
end

class ArtistTrack < ActiveRecord::Base
  belongs_to :artist
  belongs_to :track
  belongs_to :artistic_role
end

class Artist < ActiveRecord::Base
  has_many :artist_tracks
  has_many :tracks, :through => :artist_tracks
end

寻找作品

# artist_tracks.artistic_role_id is properly set to "1"
2.0.0p195 :003 > Track.last.owning_artists

  Track Load (1.1ms)  SELECT "tracks".* FROM "tracks" ORDER BY "tracks"."id" DESC LIMIT 1
  Artist Load (0.8ms)  SELECT "artists".* …