Switch to strategy

 

namespace RefactoringLib.SwitchToStrategy.Before

{

    public class ClientCode

    {

        public decimal CalculateShipping()

        {

            ShippingInfo shippingInfo = new ShippingInfo();

            return shippingInfo.CalculateShippingAmount(State.Alaska);

        }

    }



    public enum State

    {

        Alaska,

        NewYork,

        Florida

    }



    public class ShippingInfo

    {

        public decimal CalculateShippingAmount(State shipToState)

        {

            switch (shipToState)

            {

                case State.Alaska:

                    return GetAlaskaShippingAmount();



                case State.NewYork:

                    return GetNewYorkShippingAmount();



                case State.Florida:

                    return GetFloridaShippingAmount();



                default:

                    return 0m;

            }

        }



        private decimal GetAlaskaShippingAmount()

        {

            return 15m;

        }



        private decimal GetNewYorkShippingAmount()

        {

            return 10m;

        }



        private decimal GetFloridaShippingAmount()

        {

            return 3m;

        }

    }

}

View Code

 

namespace RefactoringLib.SwitchToStrategy.End

{

    public class ClientCode

    {

        public decimal CalculateShipping()

        {

            ShippingInfo shippingInfo = new ShippingInfo();

            return shippingInfo.CalculateShippingAmount(State.Alaska);

        }

    }



    public enum State

    {

        Alaska,

        NewYork,

        Florida

    }



    public class ShippingInfo

    {

        public IDictionary<State, IShippingCalculaton> ShippingCalculatons { get; set; }



        public ShippingInfo()

        {

            ShippingCalculatons = new Dictionary<State, IShippingCalculaton> 

            {

                { State.Alaska, new AlaskaShippingCalculation() },

                { State.NewYork, new NewYorkShippingCalculation() },

                { State.Florida, new FloridaShippingCalculation() }

            };

        }



        public decimal CalculateShippingAmount(State state)

        {

            return ShippingCalculatons[state].Calculate();

        }

    }



    public interface IShippingCalculaton

    {

        decimal Calculate();

    }



    public class AlaskaShippingCalculation : IShippingCalculaton

    {

        public decimal Calculate()

        {

            return 15m;

        }

    }



    public class NewYorkShippingCalculation : IShippingCalculaton

    {

        public decimal Calculate()

        {

            return 10m;

        }

    }



    public class FloridaShippingCalculation : IShippingCalculaton

    {

        public decimal Calculate()

        {

            return 5m;

        }

    }

}

View Code

 

 参考：Refactoring Day 11 : Switch to Strategy