One to Many Association Object Will Not Save - ruby-on-rails

Question

I set up a has_many belongs_to relationship in my two models and followed Ryan Bates' screencast on how to set up the controller. When I submit my form to create the new object, the nested object does not save for some reason. Here are my models:
class Auction < ActiveRecord::Base
has_many :bids, dependent: :destroy
end
class Bid < ActiveRecord::Base
belongs_to :auction
belongs_to :user
default_scope -> { order(created_at: :desc) }
validates :user_id, presence: true
validates :auction_id, presence: true
end
and my nested object controller:
class BidsController < ApplicationController
def index
#auction = Auction.find(params[:auction_id])
#bids = #auction.bids
end
def new
#auction = Auction.find(params[:auction_id])
#bid = #auction.bids.build
end
def create
#auction = Auction.find(params[:auction_id])
#bid = #auction.bids.create(params[:bid])
#bid.save
if #bid.save
flash[:success] = "Bid has been successfully placed."
else
#bid.errors
render 'new'
end
end
def destroy
#auction = Auction.find(params[:auction_id])
#bid = #auction.bids.find
#bid.destroy
flash[:notice] = "Successfully destroyed Bid."
redirect_to auction_url(#bid.article_id)
end
end
my form:
<h1>Create a New Bid</h1>
<%= form_for ([#auction, #bid]) do |f|%>
<p>
<%= f.submit %>
</p>
<%end%>
and my terminal output:
Started POST "/auctions/1/bids" for 127.0.0.1 at 2014-11-30 17:59:13 -0600
Processing by BidsController#create as HTML
Parameters: {"utf8"=>"✓", "authenticity_token"=>"dkZBcab1rgZjtJGF3LAJ//exK6liglZ0Fy4mg7HWEt0=", "commit"=>"Create Bid", "auction_id"=>"1"}
Auction Load (0.1ms) SELECT "auctions".* FROM "auctions" WHERE "auctions"."id" = ? LIMIT 1 [["id", 1]]
(0.0ms) begin transaction
(0.0ms) commit transaction
(0.0ms) begin transaction
(0.0ms) rollback transaction
(0.0ms) begin transaction
(0.0ms) rollback transaction
Thanks for your help.

Answer 1

Your bid object needs a user_id because you have validates :user_id, presence: true in the class definition.
When you call #bid.save in the controller, however, #bid does not have a user_id value, therefore the transaction gets rolled back because of the failing validation.
You should be able to see this by looking at #bid.errors.full_messages in the create action, after you've called #bid.save. (Look up the pry gem if you're not already familiar with it...it would be a perfect tool to let you do this inspection.)
Try replacing your create action with this:
def create
#auction = Auction.find(params[:auction_id])
#bid = #auction.bids.new params[:bid].merge(user_id: current_user.id)
if #bid.save
flash[:success] = "Bid has been successfully placed."
else
flash[:error] = #bid.errors.full_messages.join('. ')
render 'new'
end
end
This assumes that you have access to the current user in the controller as current_user. Devise and other popular auth solutions supply this, or you can do so yourself.
Note also that your original code tries to write #bid to the database 3 separate times, which is twice more than you need to. Here are the offending lines:
def create
...
#bid = #auction.bids.create(params[:bid])
#bid.save
if #bid.save
...
#create instantiates an object and attempts to write it to the database. In my code above, I've replaced #auction.bids.create(params...) with #auction.bids.new(params...). This initializes #bid without trying to persist it to the db.
I also removed the first #bid.save because the line below it if #bid.save will accomplish the same thing.
Finally, your line #bid.errors doesn't do anything useful. I modified it to store the error messages in your flash hash, which you can then use in your view to display the errors to the user.