31天重构指南之十三：提取方法对象

这篇文章要说的重构来自于Martin Fowlwrs的重构列表，你可以在这里查看原始描述

这是一个不常用的重构。当你发现一个方法中存在过多的局部变量时，你可以通过使用“提取方法对象”重构来引入一些方法，每个方法完成任务的一个步骤，这样可以使得程序更具有可读性。

    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: }

下面是重构后的代码中，我们引入了OrderCalculator类，该类实现了所有的计算方法，Order类将自身传递给OrderCalculator类并调用Calculate方法完成计算。

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: }

原文链接：http://www.lostechies.com/blogs/sean_chambers/archive/2009/08/13/refactoring-day-13-extract-method-object.aspx

 

PS:我个人不是很喜欢重构，我还是喜欢提取方法这个重构。