策略模式重构switch/case分支代码

Posted 2021-12-23 zhiyong-itnote

通过策略模式来重构优化代码里面的switch/case分支代码。极大程度上提高了程序的扩展性。当然，如果分支比较多，每次都需要新增加一个类，这的确是有点麻烦，可以考虑使用反射来实现。
代码：

namespace DP

    public enum State
    
        Alaska,
        NewYork,
        Florida
    

    // 抽象
    //public interface IShippingInfo
    //
    //    decimal Calculate(State state);
    //

    public class CalculateShippingAmount 
    
        public CalculateShippingAmount(IDictionary<State, IGetShippingAmount> dic) => _dic = dic;

        private IDictionary<State, IGetShippingAmount> _dic  get; set; 

        public decimal Calculate(State state) => _dic[state].GetAmount();
    

    public interface IGetShippingAmount
    
        decimal GetAmount();
    

    #region 具体地址的实现
    // 具体
    public class GetAlaskaShippingAmount : IGetShippingAmount
    
        public decimal GetAmount() => 15;
    

    public class GetNewYorkShippingAmount : IGetShippingAmount
    
        public decimal GetAmount() => 10;
    

    public class GetFloridaShippingAmount : IGetShippingAmount
    
        public decimal GetAmount() => 3;
    
    #endregion

调用：

#region 策略模式重构 switch...case...
        static void SwitchToStrategy()
        
            var dic = new Dictionary<State, IGetShippingAmount>
            
                State.Alaska,  new GetAlaskaShippingAmount() ,
                State.Florida, new GetFloridaShippingAmount() ,
                State.NewYork, new GetNewYorkShippingAmount() 
            ;

            var calculate = new CalculateShippingAmount(dic);
            var result = calculate.Calculate(State.Florida);
            Console.WriteLine($"State.Florida.ToString()返回result");
        
        #endregion

参考：使用策略模式重构switch case 代码