Question

I have got two models, User and Event. I need two kind of relationship between User and Event.

• User (:as organizer) <——-> Event, many to many relationship
• User (:as attendee) <——-> Event, many to many relationship

I am guessing if two different has_many_and_belongs_to association with polymorphism can be used to implement the relations. I am new to rails so I would appreciate any help regarding the problem.

Answer 1

You will not need a polymorphic relationship for this.

To define two associations between two models, you can do something like:

class User 
  has_many :organized_events, foreign_key: :organizer_id, class_name: "Event"
  has_many :attended_events, foreign_key: :attendee_id, class_name: "Event"
end

class Event
  belongs_to :organizer, class_name: "User"
  belongs_to :attendee, class_name: "User"
end

This will give you a one to many relationship.

If you need many to many, you’ll need a join table for each association.

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

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

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

And something similar for the event organizer association.

See my question here