Application Controller

class ApplicationController < ActionController::Base
	#This is the base application controller in which the current user is held and various other methods
  	protect_from_forgery
  	helper_method :current_user, :vat
  	def vat(income)
		vat = (income / 100) * 20
		return vat
	end
  private
	def current_user
	  @current_user ||= User.find(session[:user_id]) if session[:user_id]
	end
end

Application Helper

module ApplicationHelper
  def link_to_add_fields(name, f, association)
    new_object = f.object.send(association).klass.new
    id = new_object.object_id
    fields = f.fields_for(association, new_object, child_index: id) do |builder|
      render(association.to_s.singularize + "_fields", f: builder)
    end
    link_to(name, '#', onClick: "return false", class: "add_fields", data: {id: id, fields: fields.gsub("\n", "")})
  end
end

Javascript Add and Remove

function remove_fields(link) {
  $(link).previous("input[type=hidden]").value = "1";
  $(link).up(".fields").hide();
}

function add_fields(link, association, content) {
  var new_id = new Date().getTime();
  var regexp = new RegExp("new_" + association, "g")
  $(link).mouseup().insert({
    before: content.replace(regexp, new_id)
  });
}

New Order View

<% if current_user %>
	<div id="dashboard">
		<div id="logo"></div>
		<table id="go_back_link_container">
			<tr>
				<td>
					<div class="go_back_link">
						<%= link_to "<- Go Back", "/orders/view" %>
					</div>
				</td>
				<td>
					<div id="user_display">
						Logged in as <%= current_user.email %>.
						<%= link_to "Log out", log_out_path %>
					</div>
				</td>
			</tr>
		</table>
		<%= form_for @order, method: :post do |f| %>
			<% if @order.errors.any? %>
				<div class="error_messages">
					<% for message in @order.errors.full_messages %>
						* <%= message %> <br>
					<% end %>
				</div>
			<% end %>
			<p>
				<%= f.label 'Select The Client' %><br />
				<% if current_user.account_type != 2 %>
					<%= select :order, :client_id, Client.where("affiliated_by = #{current_user.id}").collect { |c| [ (c.firstname + " " + c.surname), c.id ] } %>
				<% else %>
					<%= select :order, :client_id, Client.all().collect { |c| [ (c.firstname + " " + c.surname), c.id ] } %>
				<% end %>
			</p>

			<%= f.fields_for :orderedproducts do |pf| %>
			<% end %>

			<%= link_to_add_fields "Add Product", f, :orderedproducts %>
			<p>
				<%= f.label 'Date of Delivery' %><br />
				<%= f.date_select :delivery_date, :order => [:day, :month, :year]%>
			</p>
			<%= f.hidden_field :user_id, value: current_user.id %>
		  	<p class="button"><%= f.submit data: { confirm: "Are you sure?" } %></p>
		<% end %>
		<% flash.each do |name, msg| %>
			<%= content_tag :div, "* " + msg, :id => "flash_#{name}" %><br />
		<% end %>
		<div id="copyright-notice"><div id="copyright_border">Copyright © Conner McCabe, all rights reserved.</div></div>
	</div>
<% else %>
	<script type="text/javascript">
		window.location="<%= root_url %>"
	</script>
<% end %>

Order Model

class Order < ActiveRecord::Base
	has_many :orderedproducts
	has_many :products, through: :orderedproducts
	has_one :client

	attr_accessible :client_id, :order_total, :approved, :delivery_date, :orderedproducts, :orderedproducts_attributes, :user_id

	accepts_nested_attributes_for :orderedproducts, :allow_destroy => true
	
	validates_presence_of :orderedproducts
	before_save :validate_quantity
	before_save :generate_total

	def generate_total
		self.order_total = self.orderedproducts.map(&:total_price).sum
	end
	def validate_quantity
		orderedproducts.each do |orderedproduct|
			orderedproduct.quantity_ordered = 1 if orderedproduct.quantity_ordered < 1
		end
	end
end

Ordered Product Fields

<fieldset style="border: none;">
	<%= select_tag(:orderedproducts, options_from_collection_for_select(@products, "id", "product_name")) %>
	<% text_field_tag(:quantity_ordered, :value => "Qty", :onfocus => "clearValue(this)", :onblur => "restoreValue(this)", :style => "width: 60px;") %>

	<%= hidden_field_tag(:_destroy) %>
	<%= link_to "remove", '#', class: "remove_fields" %>
</fieldset>

Ordered Product Model

class Orderedproduct < ActiveRecord::Base
	attr_accessible :order_id, :product_id, :quantity_ordered, :total_price
	belongs_to :order
	belongs_to :product

	before_save :total_price

  	def product_price
		product.product_price
	end
	def total_price
		product_price * quantity_ordered
	end
end

Orders Controller

class OrdersController < ApplicationController
	def view
		unless current_user.account_type == 2
			@orders = Order.where("user_id = #{current_user.id}")
		end
		@orders ||= Order.all
	end

	def new
		@order = Order.new
		@orderedproducts = Orderedproduct.new
		@suppliers = Supplier.all
	  	@products = Product.all
	end
	def create
	  	@order = Order.new(params[:order])
		if @order.save
			@order.orderedproducts.each do |orderedproduct|
				@product = Product.find(orderedproduct.product_id)
				@product.update_attributes(:product_quantity => (@product.product_quantity - orderedproduct.quantity_ordered)) unless orderedproduct.quantity_ordered > @product.product_quantity
			end
			redirect_to '/orders/view', :notice => "Order Created!"
		else
			render "new"
		end
	end
	def show
		@order = Order.find(params[:id])
		@client = Client.find(@order.client_id)
		@orderedproducts = Orderedproduct.where(:order_id => @order.id)
		@salesperson = User.find(@order.user_id)
	end
	def update
		@order = Order.find(params[:id])
		session[:return_to] ||= request.referer
		@order.update_attributes(params[:order])
		if @order.save
	    	redirect_to session[:return_to], :notice => "Order Updated!"
		else
			render "/users/view"
		end
	end
	def destroy
		@order = Order.find(params[:id])
		session[:return_to] ||= request.referer
		if @order.destroy
	    	redirect_to session[:return_to], :notice => "Order Deleted!"
		else
			redirect_to session[:return_to], :flash => "Order Could Not Be Deleted!"
		end
	end
end

Product Model

class Product < ActiveRecord::Base
	#This line makes these elements accessible outside of the class.
	attr_accessible :product_name, :product_price, :product_quantity, :supplier_id

	has_many :orderedproducts
	#has_many :orders, through: :orderedproducts
	belongs_to :supplier

	#These attributes ensure that the data entered for each element is valid and present.
	validates_presence_of :product_name
	validates_presence_of :product_price
	validates_numericality_of :product_price
	validates_presence_of :product_quantity
	validates_numericality_of :product_quantity
	validates_presence_of :supplier_id
end

Products Javascript

# Place all the behaviors and hooks related to the matching controller here.
# All this logic will automatically be available in application.js.
# You can use CoffeeScript in this file: http://jashkenas.github.com/coffee-script/
$(document).on 'click', 'form .remove_fields', (event) ->
  $(this).prev('input[type=hidden]').val('1')
  $(this).closest('fieldset').hide()
  event.preventDefault()

$(document).on 'click', 'form .add_fields', (event) ->
  time = new Date().getTime()
  regexp = new RegExp($(this).data('id'), 'g')
  $(this).before($(this).data('fields').replace(regexp, time))
  event.preventDefault()