重构第22天分解方法(Break Method)

理解：如果一个功能，里面比较复杂，代码量比较多，我们就可以把这个功能分解成多个小的method，每个方法实现该功能的一个小小的部分，并且方法命名成容易理解，和方法内容相关的名称，更有助于维护和可读性提高。

详解：

重构前代码：

 1 using System;
 2 using System.Collections;
 3 using System.Collections.Generic;
 4 using System.Linq;
 5 using System.Text;
 6 
 7 namespace ReflectorDemo
 8 {
 9     public class CashRegister
10     {
11         public CashRegister()
12         {
13             Tax = 0.06m;
14         }
15 
16         private decimal Tax { get; set; }
17 
18         public void AcceptPayment(Customer customer, IEnumerable<Product> products, decimal payment)
19         {
20             decimal subTotal = 0m;
21             foreach (Product product in products)
22             {
23                 subTotal += product.Price;
24             }
25 
26             foreach (Product product in products)
27             {
28                 subTotal -= product.AvailableDiscounts;
29             }
30 
31             decimal grandTotal = subTotal * Tax;
32 
33             customer.DeductFromAccountBalance(grandTotal);
34         }
35     }
36 
37     public class Customer
38     {
39         public void DeductFromAccountBalance(decimal amount)
40         {
41             // deduct from balance
42         }
43     }
44 
45     public class Product
46     {
47         public decimal Price { get; set; }
48         public decimal AvailableDiscounts { get; set; }
49     }
50 }

我们看到这个AcceptPayment方法，因为现实中AcceptPayment方法不会做这么多的事情。，所以我们通过几次分解将 AcceptPayment拆分成若干个名字有意义且可读性更好的小方法。

重构后代码：

 1 using System;
 2 using System.Collections;
 3 using System.Collections.Generic;
 4 using System.Linq;
 5 using System.Text;
 6 
 7 namespace ReflectorDemo
 8 {
 9     public class CashRegister
10     {
11         public CashRegister()
12         {
13             Tax = 0.06m;
14         }
15 
16         private decimal Tax { get; set; }
17         private IEnumerable<Product> Products { get; set; }
18 
19         public void AcceptPayment(Customer customer, IEnumerable<Product> products, decimal payment)
20         {
21             decimal subTotal = CalculateSubtotal();
22 
23             subTotal = SubtractDiscounts(subTotal);
24 
25             decimal grandTotal = AddTax(subTotal);
26 
27             SubtractFromCustomerBalance(customer, grandTotal);
28         }
29  private void SubtractFromCustomerBalance(Customer customer, decimal grandTotal)
30         {
31             customer.DeductFromAccountBalance(grandTotal);
32         }
33 
34         private decimal AddTax(decimal subTotal)
35         {
36             return subTotal * Tax;
37         }
38 
39         private decimal SubtractDiscounts(decimal subTotal)
40         {
41             foreach (Product product in Products)
42             {
43                 subTotal -= product.AvailableDiscounts;
44             }
45             return subTotal;
46         }
47 
48         private decimal CalculateSubtotal()
49         {
50             decimal subTotal = 0m;
51             foreach (Product product in Products)
52             {
53                 subTotal += product.Price;
54             }
55             return subTotal;
56         }
57     }
58 public class Customer
59     {
60         public void DeductFromAccountBalance(decimal amount)
61         {
62             // deduct from balance
63         }
64     }
65 
66     public class Product
67     {
68         public decimal Price { get; set; }
69         public decimal AvailableDiscounts { get; set; }
70     }
71 }

我们把AcceptPayment的内部逻辑拆分成了CalculateSubtotal、SubtractDiscounts、AddTax、SubtractFromCustomerBalance四个功能明确且可读性更好的小方法。

这个重构和我们前面讲的“提取方法”和“提取方法对象”如出一辙，尤其是“提取方法”，所以大家只要知道用这种思想重构就行。

重构第22天 分解方法(Break Method)

重构第22天分解方法(Break Method)