Rails first or initialize not working - ruby-on-rails

Question

I have a product.
I have an order.
I have a booking in between.
Whenever I make a booking from the product to the order it saves a new unique booking.
It should:
Save a new booking when it's the first made from this product.
Not make a new booking, but find and overwrite an old one, if the product has already been booked once.
If the product has already been booked on the order, but no changes are made, no database transactions are made.
def create
#order = current_order
#booking = #order.bookings.where(product_id: params[:product_id]).first_or_initialize
product = #booking.product
if #booking.new_record?
#booking.product_name = product.name
#booking.product_price = product.price
else
#booking.product_quantity = params[:product_quantity]
#booking.save
#order.sum_all_bookings
#order.save
end
Doesn't work.
Following worked:
def create
#booking = #order.bookings.find_by(product_id: params[:booking][:product_id])
if #booking
#booking.product_quantity = params[:booking][:product_quantity]
#booking.save
else
#booking = #order.bookings.new(booking_params)
#product = #booking.product
#booking.product_name = #product.name
#booking.product_price = #product.price
end
#order.save
end
Apparently I needed to grab the params, by adding [:booking] like in params[:booking][:product_id]. Anybody knows why?

Answer 1

You can try
#order.bookings.find_or_initialize_by(product_id: params[:product_id]).tap do |b|
# your business logic here
end

Answer 2

To avoid duplicates you should setup relations properly and using a database index to ensure uniqueness.
class Order
has_many :bookings
has_many :products, though: :bookings
end
class Booking
belongs_to :order
belongs_to :product
validates_uniqueness_of :order_id, scope: :product_id
end
class Product
has_many :bookings
has_many :orders, though: :bookings
end
The validation here will prevent inserting duplicates on the application level. However it is still prone to race conditions.
class AddUniquenessContstraintToBooking < ActiveRecord::Migration[5.0]
def change
add_index :bookings, [:order_id, :product_id], unique: true
end
end
However the rest of you controller logic is muddled and overcomplicated. I would distinct routes for update and create:
class BookingsController < ApplicationController
before_action :set_order, only: [:create, :index]
before_action :set_order, only: [:create, :index]
# POST /orders/:order_id/bookings
def create
#booking = #order.bookings.new(booking_params)
if #booking.save
redirect_to #order
else
render :new
end
end
# PATCH /bookings/:id
def update
if #booking.update(:booking_params)
redirect_to #order
else
render :edit
end
end
private
def set_order
#order = Order.find(params[:id])
end
def set_booking
#booking = Booking.find(params[:id])
end
def booking_params
params.require(:booking)
.permit(:product_id)
end
end
Another alternative is to use accepts_nested_attributes - but try to keep it simple.