重构第四天 : 用多态替换条件语句（if else & switch)
面相对象的一个核心基础就是多态，当你要根据对象类型的不同要做不同的操作的时候，一个好的办法就是采用多态，把算法封装到子类当中去。
重构前代码：
1 public abstract class Customer 2 { 3 } 4 5 public class Employee : Customer 6 { 7 } 8 9 public class NonEmployee : Customer 10 { 11 } 12 13 public class OrderProcessor 14 { 15 public decimal ProcessOrder(Customer customer, IEnumerable<Product> products) 16 { 17 // do some processing of order 18 decimal orderTotal = products.Sum(p => p.Price); 19 20 Type customerType = customer.GetType(); 21 if (customerType == typeof(Employee)) 22 { 23 orderTotal -= orderTotal * 0.15m; 24 } 25 else if (customerType == typeof(NonEmployee)) 26 { 27 orderTotal -= orderTotal * 0.05m; 28 } 29 30 return orderTotal; 31 } 32 }
重构后的代码：
1 public abstract class Customer 2 { 3 public abstract decimal DiscountPercentage { get; } 4 } 5 6 public class Employee : Customer 7 { 8 public override decimal DiscountPercentage 9 { 10 get { return 0.15m; } 11 } 12 } 13 14 public class NonEmployee : Customer 15 { 16 public override decimal DiscountPercentage 17 { 18 get { return 0.05m; } 19 } 20 } 21 22 public class OrderProcessor 23 { 24 public decimal ProcessOrder(Customer customer, IEnumerable<Product> products) 25 { 26 // do some processing of order 27 decimal orderTotal = products.Sum(p => p.Price); 28 29 orderTotal -= orderTotal * customer.DiscountPercentage; 30 31 return orderTotal; 32 } 33 }优质内容筛选与推荐>>
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