3 model association in rails 3 - ruby-on-rails-3

Question

i'm working on classified portal in which i have following 3 models
User (name,email)
Advertisement (title,body,user_id)
Bid (user_id,ad_id,price)
i have association between User and Advertisement as follow
class User < ActiveRecord::Base
has_many :advertisements
end
class Advertisement < ActiveRecord::Base
belongs_to :user
end
Now i wanna define Bid model , i guess this is how it should look like ,
class Bid < ActiveRecord::Base
belongs_to :user
belongs_to :advertisement
end
and i should add has_many :bids in User and Advertisement model as well(i think so),
Now my question is, say User is logged in and he wants to bid for some advertisement , so on advertisements show page how should i integrate this bid form, and please do let me how should i define routes for this .
Rails 3.2.13
Ruby 2.0.0p0
Thanks

Answer 1

Take a look at business logic of your app, there are two stories you have to implement
1) User can create advertisements (offers) (thats why you added user_id in Advertisement)
2) And user can bid on advertisements (thats simple has_many :through association)
class User < ActiveRecord::Base
has_many :bids
has_many :advertisements, :through => :bids
has_many :offers, class_name: "Advertisement", foreign_key: :user_id
end
class Advertisement < ActiveRecord::Base
belongs_to :author, class_name:"User", foreign_key: :user_id
has_many :bids
has_many :users, :through => :bids
end
class Bid < ActiveRecord::Base
belongs_to :user
belongs_to :advertisement
end
So now, if you want to get Advertisement author you need to call
a = Advertisement.last
a.author
User Load (0.1ms) SELECT "users".* FROM "users" WHERE "users"."id" = 1 LIMIT 1
=> #<User id: 1, created_at: "2013-05-31 06:13:20", updated_at: "2013-05-31 06:13:20">
a.users
User Load (0.1ms) SELECT "users".* FROM "users" INNER JOIN "bids" ON "users"."id" = "bids"."user_id" WHERE "bids"."advertisement_id" = 2
=> [#<User id: 1, created_at: "2013-05-31 06:13:20", updated_at: "2013-05-31 06:13:20">, #<User id: 1, created_at: "2013-05-31 06:13:20", updated_at: "2013-05-31 06:13:20">]
See, it makes last select through joining bids, while first one just selecting from users table. Now it works like you expect it to work.
Anyway, answering your question:
Yes, you need to define new route like this:
resources :advertisements do
member do
post 'bid'
end
end
You need to create custom action in your AdvertisementsController which will do that:
def bid
#advertisement = Advertisement.find(params[:id])
current_user.bids << Bid.new(advertisement: #advertisement, value: params[:bid])
# you may also add some value column in bids table, thats up to you
redirect_to #advertisement
end
and form would be like this:
<%= form_tag(bid_advertisement_path(#advertisement), :method => "post",) do %>
<%= label_tag(:bid, "Make a bid:") %>
<%= text_field_tag(:bid) %>
<%= submit_tag("Submit") %>
<% end %>

Answer 2

If I am correct what you may want to have is a nested_form the gem for this can do exactly what you want. I say that you may have to use a nested form because by going by what you are saying a User has_many :bids which is correct. In order for the bids to accept the attributes from the user you will need to have accepts_nested_attributes_for :user on your Bids model. Tried to mock an example together for you
<%= form_for bid do |f| %>
<%= fields_for :user do |user_fields| %>
<%= user_fields.label :name %>
<%= user_fields.text_field :name %>
<% end %>
<%= f.label :product %>
<%= f.text_field :product %>
<div class="actions">
<%= f.submit %>
</div>
<% end %>
Relevant links: 196 - Railscasts Nested Form