大话设计-简单工厂

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实现简单计算器的加减乘除运算，做到可维护、可扩展、可复用、且灵活。

可维护举例：业务人员要求加法功能只允许绝对值相加，这时修改代码的区域应只有加法，附近没有其他运算，避免不小心改到了别的运算。

可扩展举例：加个开平方根运算，添加代码的区域附近没有其他运算。

这个简单工厂用于返回运算的实例、每当有新的运算加入，工厂里的switch分支也要添加。

using system;

namespace consoleapp4
{
    class program
    {
        public static void main(string[] args)
        {
            var operation = operationfactory.getoperation("+");
            operation.numbera = convert.todouble(console.readline());
            operation.numberb = convert.todouble(console.readline());
            console.writeline(operation.getresult());

            console.readline();
        }
    }

    //运算基类
    public class operation
    {
        private double numbera;
        public double numbera
        {
            get { return numbera; }
            set { numbera = value; }
        }

        private double numberb;
        public double numberb
        {
            get { return numberb; }
            set { numberb = value; }
        }

        public virtual double getresult()
        {
            double result = 0;
            return result;
        }
    }
    public class operationadd : operation
    {
        public override double getresult()
        {
            return numbera + numberb;
        }
    }

    public class operationsub : operation
    {
        public override double getresult()
        {
            return numbera - numberb;
        }
    }

    public class operationmul : operation
    {
        public override double getresult()
        {
            return numbera * numberb;
        }
    }

    public class operationdiv : operation
    {
        public override double getresult()
        {
            if (numberb == 0)
            {
                throw new dividebyzeroexception();
            }
            return numbera / numberb;
        }
    }

    // 简单工厂
    public class operationfactory
    {
        public static operation getoperation(string operation)
        {
            switch (operation)
            {
                case "+":return new operationadd();
                case "-":return new operationsub();
                case "*":return new operationmul();
                case "/":return new operationdiv();
                default:return new operation();
            }
        }
    }
}

 

 超市结账优惠，打折或满减。

using system;

namespace consoleapp4
{
    class program
    {
        public static void main(string[] args)
        {
            var cashsuper = cashfactory.createcashsuper("8折");
            cashsuper.acceptcash(900d);
        }
    }

    public abstract class cashsuper
    {
        public abstract double acceptcash(double money);
    }

    public class cashnormal : cashsuper
    {
        public override double acceptcash(double money)
        {
            return money;
        }
    }

   public class cashrebate : cashsuper
    {
        private double rebate;

        public cashrebate(double rebate)
        {
            this.rebate = rebate;
        }

        public override double acceptcash(double money)
        {
            return money * rebate;
        }
    }

    public class cashreturn : cashsuper
    {
        private double moneycondition;
        private double moneyreturn;
        public cashreturn(double condition,double @return)
        {
            moneycondition = condition;
            moneyreturn = @return;
        }
        public override double acceptcash(double money)
        {
            if (money >= moneycondition)
            {
                return money - ((money / moneycondition) * moneyreturn);
            }
            else
            {
                return money;
            }
        }
    }

    public class cashfactory
    {
        public static cashsuper createcashsuper(string type)
        {
            switch (type)
            {
                case "满300减50":return new cashreturn(300d, 50d);
                case "8折":return new cashrebate(0.8d);
                default:return new cashnormal();
            }
        }
    }   
}