Rails 4.0 undefined method `+' for nil:NilClass - ruby-on-rails

Question

I'm trying to add a line to my orders_items controller so if its a new order to increment the counter from zero to one. so have created an action that does that before the save is called but when I try it I get:
undefined method `+' for nil:NilClass
def create
#order_item = #order.order_items.find_or_initialize_by_product_id(params[:product_id])
# Error below
#order_item.quantity += 1
respond_to do |format|
if #order_item.save
end
end
order_item.rb:
class OrderItem < ActiveRecord::Base
belongs_to :order
belongs_to :product
validates :order_id, :product, presence: true
validates :quantity, numericality: { only_integer: true, greater_than: 0 }
def subtotal
quantity * product.price
end
end
order_items_controller.rb:
class OrderItemsController < ApplicationController
before_action :set_order_item, only: [:show, :edit, :destroy]
before_action :load_order, only: [:create]
# GET /order_items
# GET /order_items.json
def index
#order_items = OrderItem.all
end
# GET /order_items/new
def new
#order_item = OrderItem.new
end
# POST /order_items
# POST /order_items.json
def create
#order_item = #order.order_items.find_or_initialize_by_product_id(params[:product_id])
#order_item.quantity += 1
respond_to do |format|
if #order_item.save
format.html { redirect_to #order, notice: 'Successfully added product to cart.' }
format.json { render action: 'show', status: :created, location: #order_item }
else
format.html { render action: 'new' }
format.json { render json: #order_item.errors, status: :unprocessable_entity }
end
end
end
# PATCH/PUT /order_items/1
# PATCH/PUT /order_items/1.json
def update
#order_item = OrderItem.find(params[:id])
respond_to do |format|
if order_item_params[:quantity].to_i == 0
#order_item.destroy
format.html { redirect_to #order_item.order, notice: 'Order item was successfully updated.' }
format.json { head :no_content }
elsif #order_item.update(order_item_params)
format.html { redirect_to #order_item.order, notice: 'Successfully updated the order item.' }
format.json { head :no_content }
else
format.html { render action: 'edit' }
format.json { render json: #order_item.errors, status: :unprocessable_entity}
end
end
end
# DELETE /order_items/1
# DELETE /order_items/1.json
def destroy
#order_item.destroy
respond_to do |format|
format.html { redirect_to #order_item.order }
format.json { head :no_content }
end
end
private
# Use callbacks to share common setup or constraints between actions.
def load_order
#order = Order.find_or_initialize_by_id(session[:order_id], status: "unsubmitted")
if #order.new_record?
#order.save!
session[:order_id] = #order.id
end
end
def set_order_item
#order_item = OrderItem.find(params[:id])
end
# Never trust parameters from the scary internet, only allow the white list through.
def order_item_params
params.require(:order_item).permit(:product_id, :order_id, :quantity)
end
end
Migration file:
class AddDefaultQuantityToOrderItems < ActiveRecord::Migration
def change
change_column :order_items, :quantity, :integer, default: 0
end
end
rails console:
#order.order_items.find_or_initialize_by_product_id(params[:product_id])
NoMethodError: undefined method `order_items' for nil:NilClass
from (irb):1
from /usr/local/rvm/gems/ruby-2.0.0-p247/gems/railties-4.0.4/lib/rails/commands/console.rb:90:in `start'
from /usr/local/rvm/gems/ruby-2.0.0-p247/gems/railties-4.0.4/lib/rails/commands/console.rb:9:in `start'
from /usr/local/rvm/gems/ruby-2.0.0-p247/gems/railties-4.0.4/lib/rails/commands.rb:62:in `<top (required)>'
from bin/rails:4:in `require'
from bin/rails:4:in `<main>'
Model order.rb:
class Order < ActiveRecord::Base
has_many :order_items, dependent: :destroy
def total
order_items.map(&:subtotal).sum
end
end
orders_controller.rb:
class OrdersController < ApplicationController
before_action :set_order, only: [:show, :edit, :update, :destroy]
# GET /orders
# GET /orders.json
def index
#orders = Order.all
end
# GET /orders/1
# GET /orders/1.json
def show
end
# GET /orders/new
def new
#order = Order.new
end
# GET /orders/1/edit
def edit
end
# POST /orders
# POST /orders.json
def create
#order = Order.new(order_params)
respond_to do |format|
if #order.save
format.html { redirect_to #order, notice: 'Order was successfully created.' }
format.json { render action: 'show', status: :created, location: #order }
else
format.html { render action: 'new' }
format.json { render json: #order.errors, status: :unprocessable_entity }
end
end
end
# PATCH/PUT /orders/1
# PATCH/PUT /orders/1.json
def update
respond_to do |format|
if #order.update(order_params)
format.html { redirect_to #order, notice: 'Order was successfully updated.' }
format.json { head :no_content }
else
format.html { render action: 'edit' }
format.json { render json: #order.errors, status: :unprocessable_entity }
end
end
end
# DELETE /orders/1
# DELETE /orders/1.json
def destroy
#order.destroy
respond_to do |format|
format.html { redirect_to products_path }
format.json { head :no_content }
end
end
private
# Use callbacks to share common setup or constraints between actions.
def set_order
#order = Order.find(params[:id])
end
# Never trust parameters from the scary internet, only allow the white list through.
def order_params
params.require(:order).permit(:user_id, :status)
end
end
Update
Rake routes shows route call for /:product_id
product.rb
class Product < ActiveRecord::Base
validates_numericality_of :price
validates :stock ,numericality: { greater_than_or_equal_to: 0 }
end
order.rb
# #Chiperific added proper 4-line indentation for SO viewing.
class OrderItem < ActiveRecord::Base
belongs_to :order
belongs_to :product
validates :order_id, :product, presence: true
validates :quantity, numericality: { only_integer: true, greater_than: 0 }
def subtotal
quantity * product.price
end
end
order items.rb
class OrderItem < ActiveRecord::Base
belongs_to :order
belongs_to :product
validates :order_id, :product, presence: true
validates :quantity, numericality: { only_integer: true, greater_than: 0 }
def subtotal
quantity * product.price
end
end
when i add
def create
#order_item = OrderItems.find_or_initialize_by_product_id(params[:product_id])
#order_item.quantity +=1
i get NameError in OrderItemsController#create - uninitialized constant OrderItemsController::Orderitems
def create
#order_item = Orderitems.find_or_initialize_by_product_id(params[:product_id]) <-error
#order_item.quantity += 1
if i try
#order = Order.find(params[:order_id])
#order_item = #order.order_items.find_or_initialize_by_product_id(params[:product_id])
#order_item.quantity += 1
i get ActiveRecord::RecordNotFound in OrderItemsController#create - Couldn't find Order without an ID
def create
#order = Order.find(params[:order_id])
#order_item = #order.order_items.find_or_initialize_by_product_id(params[:product_id])<-error
#order_item.quantity += 1

Answer 1

I don' t see where #order is defined. Since #order is null, #order_items will be as well.
I'm assuming your view URL is something like /orders/:order_id/order_items/:id
So let's use the URL parameter to make sure you get an Order or Order_ID initiated.
Option 1: Don't worry about #order
def create
#order_item = OrderItem.find_or_initialize_by_product_id(params[:product_id])
#order_item.quantity +=1
...
end
Option 2: Set the `#order` first
def create
#order = Order.find(params[:order_id])
#order_item = #order.order_items.find_or_initialize_by_product_id(params[:product_id])
#order_item.quantity += 1
...
end
Other potential problem:
.find_or_initialize_by_product_id(params[:product_id]) isn't actually finding or initializing.
It looks like this is your table relationship:
[Orders]`````\
|--> [Order_Items]
[Products]___/
I don't see where you have accepts_nested_attributes_for :order_items in orders.rb
You probably also need accepts_nested_attributes_for :order_items in products.rb
Does an Order_Item record have a Product_id field? I see where you're validating the presence of :product, but not :product_id, what does your schema look like? What happens if you try `find__or_initialize_by_product(params[:product_id])
Does your route call for /:product_id or /:product or neither? (a.k.a. is there a params[:product_id]?)
Update:
Thanks for the updated comments. Please add the whole URI being used, the whole Rake Routes line, or the Routes.rb file.
Or, while I know it's not SO-best-practice, you could post a link to the project on Github and I'll take a look there.
I'm still convinced that (at least one of) the issue(s) is that #order is not being set.
Trying it out in the Rails console is a great way to find out of .find_or_initialize_by_product_id is working
But, rails console can’t pull params and you still aren’t assigning #order first.
To test, in the rails console, try:
#order = Order.first #<----(just so you get #order assigned)
#order.order_items.find_or_initialize_by_product_id(1)
Also:
#order_item = OrderItems.find_or_initialize_by_product_id(params[:product_id])
OrderItems should be singular (my bad!!):
#order_item = OrderItem.find_or_initialize_by_product_id(params[:product_id])
I'll pay closer attention to this post and be more timely with my posts as I'm sure you're getting frustrated. Hang in there, your methodology is good.
But, there may be another way if we can't get these kinks worked out. Could we find the order item quantity by counting the # of records with a specific order id instead of saving the number statically in the database? Just a thought if you're ready to bail on this problem.

Answer 2

You can initialize #order_item.quantity by putting this in your OrderItem class:
def quantity
self.quantity ||= 0
end

Answer 3

Go into your method find_or_initialize_by_product_id, and make sure you initialize the attribute quantity to 0.
Here's a simple reproduction of your error - notice I never initialized x to 0:
$ irb
irb(main):001:0> x += 5
NoMethodError: undefined method `+' for nil:NilClass
from (irb):1
from /usr/bin/irb:11:in `<main>'

Answer 4

In Rails 4 you can use the following:
#order_item = #order.order_items.where(product_id: params[:product_id]).first_or_create
instead of
#order_item = #order.order_items.find_or_initialize_by_product_id(params[:product_id])
and this:
#order = Order.where(session[:order_id], status: "unsubmitted").first_or_initialize
instead of
#order = Order.find_or_initialize_by_id(session[:order_id], status: "unsubmitted")