Question

I’m having some problems with ruby on rails, specifically setting up a many-to-many connection with deal and event through deal_event. I’ve checked out several similar stackoverflow questions and even http://guides.rubyonrails.org/ but I’m still not getting something..

Here are my models:

deal.rb

class Deal < ActiveRecord::Base
  has_many :deal_events
  has_many :events, :through => "deal_events"
  attr_accessible :approved, :available, :cents_amount, :dollar_amount, :participants, :type
end

event.rb

class Event < ActiveRecord::Base
  has_many :deal_events
  has_many :deals, :through => "deal_events"
  attr_accessible :day, :image, :description, :location, :title, :venue, :remove_image
end

deal_event.rb

class DealEvent < ActiveRecord::Base
  belongs_to :deal
  belongs_to :event
end

And here are my migration files:

20130102150011_create_events.rb

class CreateEvents < ActiveRecord::Migration
  def change
    create_table :events do |t|
      t.string :title,     :null => false
      t.string :venue
      t.string :location
      t.text :description 
      t.date :day

      t.timestamps
    end
  end
end

20130112182824_create_deals.rb

class CreateDeals < ActiveRecord::Migration
  def change
    create_table :deals do |t|
      t.integer :dollar_amount
      t.integer :cents_amount
      t.integer :participants
      t.string  :type, :default => "Deal"
      t.integer :available
      t.string  :approved

      t.timestamps
    end
  end
end

20130114222309_create_deal_events.rb

class CreateDealEvents < ActiveRecord::Migration
  def change
    create_table :deal_events do |t|
      t.integer :deal_id, :null => false
      t.integer :event_id, :null => false

      t.timestamps
    end
  end
end

After I seed my database with one deal and one event, I go into the console and type in

deal = Deal.first # ok
event = Event.first # ok

DealEvent.create(:deal => deal, :event => event) # Error: ActiveModel::MassAssignmentSecurity::Error: Can't mass-assign protected attributes: deal, event

deal.events # Error: ActiveRecord::HasManyThroughAssociationNotFoundError: Could not find the association "deal_events" in model Deal

Any idea on what I’m doing wrong for these two errors to be popping up? Thanks.

Answer 1

You’ll need this line in your DealEvent model:

attr_accessible :deal, :event

Although if it’s just a relationship table (which it looks like) then you don’t create the relationship that way. Use nested forms and the like.