Question

I have a Join Model I just Migrated called EventUsers that has an user_id, event_id, and an attribute i created called opinion:string

  create_table :events_users, :id => false do |t|
      t.integer :user_id
      t.integer :event_id
      t.string :opinion #  extra attribute I made
  end

and
event.rb

   has_and_belongs_to_many :users

and user.rb

   has_and_belongs_to_many :events

I can add to the join model with

  @user = User.find(session[:user_id])
  @event = Event.find(params[:id])
  @user.events << @event

but before I do that…… How do I set the opinion attribute to some string and then insert?

Answer 1

If your join model has any fields other than just the foreign keys, then you shouldn’t be using a HABTM relationship. You should create an intermediate model such as Opinion and have each model related like so:

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

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

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

Update:

In order to add opinions, you will likely want to create a RESTful interface. I would start by adding a nested route within either users, events, or both

map.resources :users do |user|
  user.resources :opinions
end

Then add an opinions controller with your standard RESTful actions (new, create, edit, update, etc) and corresponding views. There are tons of resources on how to build a standard restful interface, but I would start with these:

http://guides.rubyonrails.org/routing.html#resource-routing-the-rails-default

http://guides.rubyonrails.org/routing.html#nested-resources