Question

I’m wondering…
(1) what should be the correct associations for 2 different tables both with 2 same columns
(2) how do i display the user list in views with for loop

So one table is called Attending and has 2 columns: Events & Users
Another table is called NotAttending and has 2 columns: Events & Users

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

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

class Attending < ActiveRecord::Base
  belongs_to :user
  belongs_to :event
end

class Notattending < ActiveRecord::Base
  belongs_to :user
  belongs_to :event
end

How would I display the list of users for attending and notattending in the views? I get error undefined method users for nil:NilClass

<% for user in @attending.user %>  
  <%= user.name %></br>
<% end %>

Thanks!

Answer 1

ASIDE: why not combine Attending and Nonattending into one table with three columns, event, user, and is_attending (true if attending, false if not attending)?

But no matter, let’s assume the data model is fixed…

You cannot use has_many :users twice. You could choose to make another method:

class User < ActiveRecord::Base
  has_many :attending
  has_many :notattending
  def events
    self.attending.map(&:events) + self.nonattending.map(&:events)
  end
end 

class Event < ActiveRecord::Base
  has_many :attending
  has_many :notattending
  def users
    self.attending.map(&:users) + self.nonattending.map(&:users)
  end
end