How to set up multiple aliased joins between two models?

问题

In a Rails 3.2 app I need to set up two associations between the same two models.

For example

class User
  has_many :events
  has_many :attendances
  has_many :attended_events, through: :attendances
end

class Event
  belongs_to :event_organizer, class_name: "User"
  has_many :attendances
  has_many :attendees, through: :attendances, class_name: "User"
end

class Attendance
  belongs_to :attended_event, class_name: "Event"
  belongs_to :attendee, class_name: "User"
end

This is the first time I've experimented with aliasing class names, and I'm having trouble getting it to work. I'm not sure if the issue lies with how I've defined the associations, or elsewhere.

Do my associations look OK? Have I overlooked something needed to get this to work?

The problem I'm having is that no user ids are being set in the Attendance model. This may be a stupid question, but given my associations above, should the field name be :user_id or :event_organizer_id?

Really appreciate any suggestions on this. Thanks!

回答1:

foreign_key to be specified in User and Event

class User
  has_many :events

  has_many :attendances, foreign_key: :attendee_id
  has_many :attended_events, through: :attendances
end

class Event
  belongs_to :event_organizer, class_name: "User" 
  # here it should be event_organizer_id

  has_many :attendances, foreign_key: :attended_event_id
  has_many :attendees, through: :attendances
end

class Attendance
  belongs_to :attended_event, class_name: "Event" 
  # this should have attended_event_id

  belongs_to :attendee, class_name: "User"        
  # this should have attendee_id because of 1st param to belongs_to here is "attendee"
  # and same should be added as foreign_key in User model
  # same follows for Event too
end

来源：https://stackoverflow.com/questions/10898602/how-to-set-up-multiple-aliased-joins-between-two-models