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重构第四天 : 用多态替换条件语句（if else & switch)

2024-07-10 06:05:48   222人阅读

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 : Customer10 {11 }12   13 public class OrderProcessor14 {15      public decimal ProcessOrder(Customer customer, IEnumerable<Product> products)16      {17          // do some processing of order18          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 : Customer15   {16       public override decimal DiscountPercentage17       {18           get { return 0.05m; }19       }20   }21    22   public class OrderProcessor23   {24       public decimal ProcessOrder(Customer customer, IEnumerable<Product> products)25       {26           // do some processing of order27           decimal orderTotal = products.Sum(p => p.Price);28    29           orderTotal -= orderTotal * customer.DiscountPercentage;30    31           return orderTotal;32       }33   }

 


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