Refactoring Day 13 : Extract Method Object

   1: public class OrderLineItem

   2: {

   3:     public decimal Price { get; private set; }

   4: }

   5:  

   6: public class Order

   7: {

   8:     private IList<OrderLineItem> OrderLineItems { get; set; }

   9:     private IList<decimal> Discounts { get; set; }

  10:     private decimal Tax { get; set; }

  11:  

  12:     public decimal Calculate()

  13:     {

  14:         decimal subTotal = 0m;

  15:  

  16:         // Total up line items

  17:         foreach (OrderLineItem lineItem in OrderLineItems)

  18:         {

  19:             subTotal += lineItem.Price;

  20:         }

  21:  

  22:         // Subtract Discounts

  23:         foreach (decimal discount in Discounts)

  24:             subTotal -= discount;

  25:  

  26:         // Calculate Tax

  27:         decimal tax = subTotal * Tax;

  28:  

  29:         // Calculate GrandTotal

  30:         decimal grandTotal = subTotal + tax;

  31:  

  32:         return grandTotal;

  33:     }

  34: }

   1: public class OrderLineItem

   2: {

   3:     public decimal Price { get; private set;}

   4: }

   5:  

   6: public class Order

   7: {

   8:     public IEnumerable<OrderLineItem> OrderLineItems { get; private set;}

   9:     public IEnumerable<decimal> Discounts { get; private set; }

  10:     public decimal Tax { get; private set; }

  11:  

  12:     public decimal Calculate()

  13:     {

  14:         return new OrderCalculator(this).Calculate();

  15:     }

  16: }

  17:  

  18: public class OrderCalculator

  19: {

  20:     private decimal SubTotal { get; set;}

  21:     private IEnumerable<OrderLineItem> OrderLineItems { get; set; }

  22:     private IEnumerable<decimal> Discounts { get; set; }

  23:     private decimal Tax { get; set; }

  24:  

  25:     public OrderCalculator(Order order)

  26:     {

  27:         OrderLineItems = order.OrderLineItems;

  28:         Discounts = order.Discounts;

  29:         Tax = order.Tax;

  30:     }

  31:  

  32:     public decimal Calculate()

  33:     {

  34:         CalculateSubTotal();

  35:  

  36:         SubtractDiscounts();

  37:  

  38:         CalculateTax();

  39:  

  40:         return SubTotal;

  41:     }

  42:  

  43:     private void CalculateSubTotal()

  44:     {

  45:         // Total up line items

  46:         foreach (OrderLineItem lineItem in OrderLineItems)

  47:             SubTotal += lineItem.Price;

  48:     }

  49:  

  50:     private void SubtractDiscounts()

  51:     {

  52:         // Subtract Discounts

  53:         foreach (decimal discount in Discounts)

  54:             SubTotal -= discount;

  55:     }

  56:  

  57:     private void CalculateTax()

  58:     {

  59:         // Calculate Tax

  60:         SubTotal += SubTotal * Tax;

  61:     }

  62: }