Incrementing repeated items in cart rails 4 - ruby-on-rails

Question

I am having a problem when I add items into my cart where instead of updating an item if it already exists, it creates a duplicate item. I know I need to pass a validation to check if the order_item exists but I'm not quite sure how or where to do it.
class ApplicationController < ActionController::Base
# Prevent CSRF attacks by raising an exception.
# For APIs, you may want to use :null_session instead.
protect_from_forgery with: :exception
helper_method :current_order
helper_method :current_buylist_order
def current_order
if !session[:order_id].nil?
Order.find(session[:order_id])
else
Order.new
end
end
end
class OrderItemsController < ApplicationController
def create
#order = current_order
#order_item = #order.order_items.new(order_item_params)
#order.save
session[:order_id] = #order.id
end
def update
#order = current_order
#order_item = #order.order_items.find(params[:id])
#order_item.update_attributes(order_item_params)
#order_items = #order.order_items
end
def destroy
#order = current_order
#order_item = #order.order_items.find(params[:id])
#order_item.destroy
#order_items = #order.order_items
end
private
def order_item_params
params.require(:order_item).permit(:quantity, :card_id)
end
end
class CartsController < ApplicationController
def show
#order_items = current_order.order_items
end
end
class Order < ActiveRecord::Base
belongs_to :order_status
has_many :order_items
before_create :set_order_status
before_save :update_subtotal
def subtotal
order_items.collect { |oi| oi.valid? ? (oi.quantity * oi.unit_price) : 0 }.sum
end
private
def set_order_status
self.order_status_id = 1
end
def update_subtotal
self[:subtotal] = subtotal
end
end
class OrderItem < ActiveRecord::Base
belongs_to :card
belongs_to :order
validates :quantity, presence: true, numericality: { only_integer: true, greater_than: 0 }
validate :card_present
validate :order_present
before_save :finalize
def unit_price
if persisted?
self[:unit_price]
else
card.price
end
end
def total_price
unit_price * quantity
end
private
def card_present
if card.nil?
errors.add(:card, "is not valid or is not active.")
end
end
def order_present
if order.nil?
errors.add(:order, "is not a valid order.")
end
end
def finalize
self[:unit_price] = unit_price
self[:total_price] = quantity * self[:unit_price]
end
end

Answer 1

In you OrderItemsController, in create and update methods you are using line #order_item = #order.order_items.new(order_item_params) which initializes new item every time one of these methods is called. You need to change these methods, so they create new item only if item with same params doesn't already exist. Take a look at first_or_initialize or first_or_create method. Or use a simple condition (Eg if item exists in the order increase quantity by one, else create new item)

Answer 2

In your Order Items Controller, under the create method, have a code that checks for an existing product then increments the quantity if you add to cart more than once. You can use jQuery to disable the button too.
Under the create method in order_items_controller
#product_id = params['order_item']['product_id']
#order.order_items.each do |oi|
if oi.product_id.to_s == #product_id
updater(oi.id,params['order_item']['quantity']) and return
end
end
Add and extra method for the update in quantity
def updater(id,quantity)
#order = current_order
#order_item = #order.order_items.find(id)
quantity = #order_item.quantity + quantity.to_i
#order_item.update(quantity:quantity)
#order_items = #order.order_items
end

Answer 3

What worked for me is this:
def create
#order = current_order
if OrderItem.where("card_id = ? AND order_id = ?",
params[:order_item][:card_id], #order.id.to_s).empty?
#order_item = OrderItem.new(order_item_params)
#order_item.order = current_order
#order_item.save
else
#order_item = OrderItem.where("card_id = ? AND order_id = ?",
params[:order_item][:card_id], #order.id.to_s).first
quantity = #order_item.quantity += params[:order_item][:quantity].to_i
#order_item.update(quantity: quantity)
end
end