no implicit conversion of Symbol into Integer Error with hash

Question

I get the error "no implicit conversion of Symbol into Integer"

Here is my code:

# == Schema Information
#
# Table name: my_payments
#
#  id               :integer          not null, primary key
#  email            :string
#  ip               :string
#  status           :string
#  fee              :decimal(6, 2)
#  paypal_id        :string
#  total            :decimal(8, 2)
#  created_at       :datetime         not null
#  updated_at       :datetime         not null
#  shopping_cart_id :integer
#

class MyPayment < ActiveRecord::Base
    belongs_to :shopping_cart
    include AASM 

    aasm column: "status" do
        state :created, initial: true
        state :payed
        state :failed

        event :pay do
            after do
                shopping_cart.pay!
                self.update_stock_products()
            end
            transitions from: :created, to: :payed
        end
    end

    def update_stock_products       
        self.shopping_cart.in_shopping_carts.map { |i_sh|
            product = i_sh.product
            self_product = Product.where(id: product.id)
            num = self_product[:stock]
            res = num - i_sh.num_products 
            Product.update(product.id,stock: res)                   
        }       
    end
end

The error is in the line:

num = self_product[:stock]

Answer 1

self_product is being treated as an array (or array-like thing), hence it's expecting a numeric index, not a symbol as you'd expect for a hash or active record instance.

The issue is here:

self_product = Product.where(id: product.id)

This returns an ActiveRecord Relation object. Using [] operator on it will run the query and give back the nth item.

You probably want something like:

num = Product.find(product.id).stock

However, if you have the shopping cart item association to product setup right, you shouldn't need to do that. You should be able to just do:

num = product.stock