商场促销 策略模式

2.1 商场收银软件

namespace 商场管理软件
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        double total = 0.0d;

        private void btnOk_Click(object sender, EventArgs e)
        {
            double totalPrices = Convert.ToDouble(txtPrice.Text) * Convert.ToDouble(txtNum.Text);
            total = total + totalPrices;
            lbxList.Items.Add("单价：" + txtPrice.Text + " 数量：" + txtNum.Text + " 总计：" + totalPrices.ToString());
            lblResult.Text = total.ToString();
        }

        private void btnClear_Click(object sender, EventArgs e)
        {
            total = 0d;
            txtPrice.Text = "0.00";
            txtNum.Text = "1";
            lbxList.Items.Clear();
            lblResult.Text = "0.00";
        }

    }
}

2.2 增加打折

namespace 商场管理软件
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        double total = 0.0d;

        private void Form1_Load(object sender, EventArgs e)
        {
            cbxType.Items.AddRange(new object[] { "正常收费", "打八折", "打七折", "打五折" });
            cbxType.SelectedIndex = 0;
        }

        private void btnOk_Click(object sender, EventArgs e)
        {
            double totalPrices = 0d;

            switch (cbxType.SelectedIndex)
            {
                case 0:
                    totalPrices = Convert.ToDouble(txtPrice.Text) * Convert.ToDouble(txtNum.Text);
                    break;
                case 1:
                    totalPrices = Convert.ToDouble(txtPrice.Text) * Convert.ToDouble(txtNum.Text) * 0.8;
                    break;
                case 2:
                    totalPrices = Convert.ToDouble(txtPrice.Text) * Convert.ToDouble(txtNum.Text) * 0.7;
                    break;
                case 3:
                    totalPrices = Convert.ToDouble(txtPrice.Text) * Convert.ToDouble(txtNum.Text) * 0.5;
                    break;
            }
            total = total + totalPrices;
            lbxList.Items.Add("单价：" + txtPrice.Text + " 数量：" + txtNum.Text
                + " " + cbxType.SelectedItem + " 总计：" + totalPrices.ToString());
            lblResult.Text = total.ToString();
        }

        private void btnClear_Click(object sender, EventArgs e)
        {
            total = 0d;
            txtPrice.Text = "0.00";
            txtNum.Text = "1";
            lbxList.Items.Clear();
            lblResult.Text = "0.00";
        }

    }
}

2.3 简单工厂实现

面向对象编程，并不是类越多越好，类的划分是为了封装，但分类的基础是抽象，具有相同属性和功能的对象的抽象集合才是类，

abstract class CashSuper
{
    public abstract double acceptCash(double money);
}

//正常收费
class CashNormal : CashSuper
{
    public override double acceptCash(double money)
    {
        return money;
    }
}

//返利收费
class CashReturn : CashSuper
{
    private double moneyCondition = 0.0d;
    private double moneyReturn = 0.0d;

    //初始化时必须输入返利条件和返利值，如满300返100，则moneyCondition为300，moneyReturn为100，
    public CashReturn(string moneyCondition, string moneyReturn)
    {
        this.moneyCondition = double.Parse(moneyCondition);
        this.moneyReturn = double.Parse(moneyReturn);
    }

    public override double acceptCash(double money)
    {
        double result = money;
        //若大于返利条件，则需要减去返利值
        if (money >= moneyCondition)
            result = money - Math.Floor(money / moneyCondition) * moneyReturn;
        return result;
    }
}

//打折收费
class CashRebate : CashSuper
{
    private double moneyRebate = 1d;

    //初始化时必需要输入折扣率，如八折就是0.8，
    public CashRebate(string moneyRebate)
    {
        this.moneyRebate = double.Parse(moneyRebate);
    }

    public override double acceptCash(double money)
    {
        return money * moneyRebate;
    }

}

//现金收取工厂
class CashFactory
{
    //根据条件返回相应的对象
    public static CashSuper createCashAccept(string type)
    {
        CashSuper cs = null;
        switch (type)
        {
            case "正常收费":
                cs = new CashNormal();
                break;
            case "满300返100":
                CashReturn cr1 = new CashReturn("300", "100");
                cs = cr1;
                break;
            case "打8折":
                CashRebate cr2 = new CashRebate("0.8");
                cs = cr2;
                break;
        }
        return cs;
    }

}

namespace 商场管理软件
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        double total = 0.0d;

        private void btnOk_Click(object sender, EventArgs e)
        {
            CashSuper csuper = CashFactory.createCashAccept(cbxType.SelectedItem.ToString());
            double totalPrices = 0d;
            totalPrices = csuper.acceptCash(Convert.ToDouble(txtPrice.Text) * Convert.ToDouble(txtNum.Text));
            total = total + totalPrices;
            lbxList.Items.Add("单价：" + txtPrice.Text + " 数量：" + txtNum.Text + " "
                + cbxType.SelectedItem + " 总计：" + totalPrices.ToString());
            lblResult.Text = total.ToString();
        }

        private void btnClear_Click(object sender, EventArgs e)
        {
            total = 0d;
            txtPrice.Text = "0.00";
            txtNum.Text = "0";
            lbxList.Items.Clear();
            lblResult.Text = "0.00";
        }

    }
}

2.4 策略模式

策略模式：它定义了算法家族，分别封装起来，让它们之间可以相互替换，此模式让算法的变化不会影响到使用算法的客户，

namespace 策略模式
{
    class Program
    {
        static void Main(string[] args)
        {
            Context context;

            context = new Context(new ConcreteStrategyA());
            context.ContextInterface();

            context = new Context(new ConcreteStrategyB());
            context.ContextInterface();

            context = new Context(new ConcreteStrategyC());
            context.ContextInterface();

            Console.Read();
        }
    }

    //抽象算法类
    abstract class Strategy
    {
        //算法方法
        public abstract void AlgorithmInterface();
    }

    //具体算法A
    class ConcreteStrategyA : Strategy
    {
        //算法A实现方法
        public override void AlgorithmInterface()
        {
            Console.WriteLine("算法A实现");
        }
    }

    //具体算法B
    class ConcreteStrategyB : Strategy
    {
        //算法B实现方法
        public override void AlgorithmInterface()
        {
            Console.WriteLine("算法B实现");
        }
    }

    //具体算法C
    class ConcreteStrategyC : Strategy
    {
        //算法C实现方法
        public override void AlgorithmInterface()
        {
            Console.WriteLine("算法C实现");
        }
    }

    //上下文
    class Context
    {
        Strategy strategy;

        public Context(Strategy strategy)
        {
            this.strategy = strategy;
        }

        //上下文接口
        public void ContextInterface()
        {
            strategy.AlgorithmInterface();
        }
    }

}

2.5 策略模式实现

abstract class CashSuper
{
    public abstract double acceptCash(double money);
}

//正常收费
class CashNormal : CashSuper
{
    public override double acceptCash(double money)
    {
        return money;
    }
}

//返利收费
class CashReturn : CashSuper
{
    private double moneyCondition = 0.0d;
    private double moneyReturn = 0.0d;

    //初始化时必须输入返利条件和返利值，如满300返100，则moneyCondition为300，moneyReturn为100，
    public CashReturn(string moneyCondition, string moneyReturn)
    {
        this.moneyCondition = double.Parse(moneyCondition);
        this.moneyReturn = double.Parse(moneyReturn);
    }

    public override double acceptCash(double money)
    {
        double result = money;
        //若大于返利条件，则需要减去返利值
        if (money >= moneyCondition)
            result = money - Math.Floor(money / moneyCondition) * moneyReturn;
        return result;
    }
}

//打折收费
class CashRebate : CashSuper
{
    private double moneyRebate = 1d;

    //初始化时必需要输入折扣率，如八折就是0.8，
    public CashRebate(string moneyRebate)
    {
        this.moneyRebate = double.Parse(moneyRebate);
    }

    public override double acceptCash(double money)
    {
        return money * moneyRebate;
    }

}

class CashContext
{
    private CashSuper cs;

    public CashContext(CashSuper csuper)
    {
        this.cs = csuper;
    }

    public double GetResult(double money)
    {
        return cs.acceptCash(money);
    }

}

namespace 商场管理软件
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        double total = 0.0d;

        private void btnOk_Click(object sender, EventArgs e)
        {
            CashContext cc = null;
            switch (cbxType.SelectedItem.ToString())
            {
                case "正常收费":
                    cc = new CashContext(new CashNormal());
                    break;
                case "满300返100":
                    cc = new CashContext(new CashReturn("300", "100"));
                    break;
                case "打8折":
                    cc = new CashContext(new CashRebate("0.8"));
                    break;
            }
            double totalPrices = 0d;
            totalPrices = cc.GetResult(Convert.ToDouble(txtPrice.Text) * Convert.ToDouble(txtNum.Text));
            total = total + totalPrices;
            lbxList.Items.Add("单价：" + txtPrice.Text + " 数量：" + txtNum.Text + " " + cbxType.SelectedItem + " 总计：" + totalPrices.ToString());
            lblResult.Text = total.ToString();
        }

        private void btnClear_Click(object sender, EventArgs e)
        {
            total = 0d;
            txtPrice.Text = "0.00";
            txtNum.Text = "1";
            lbxList.Items.Clear();
            lblResult.Text = "0.00";
        }

    }
}

2.6 策略与简单工厂结合

abstract class CashSuper
{
    public abstract double acceptCash(double money);
}

//正常收费
class CashNormal : CashSuper
{
    public override double acceptCash(double money)
    {
        return money;
    }
}

//返利收费
class CashReturn : CashSuper
{
    private double moneyCondition = 0.0d;
    private double moneyReturn = 0.0d;

    //初始化时必须输入返利条件和返利值，如满300返100，则moneyCondition为300，moneyReturn为100，
    public CashReturn(string moneyCondition, string moneyReturn)
    {
        this.moneyCondition = double.Parse(moneyCondition);
        this.moneyReturn = double.Parse(moneyReturn);
    }

    public override double acceptCash(double money)
    {
        double result = money;
        //若大于返利条件，则需要减去返利值
        if (money >= moneyCondition)
            result = money - Math.Floor(money / moneyCondition) * moneyReturn;
        return result;
    }
}

//打折收费
class CashRebate : CashSuper
{
    private double moneyRebate = 1d;

    //初始化时必需要输入折扣率，如八折就是0.8，
    public CashRebate(string moneyRebate)
    {
        this.moneyRebate = double.Parse(moneyRebate);
    }

    public override double acceptCash(double money)
    {
        return money * moneyRebate;
    }

}

class CashContext
{
    CashSuper cs = null;

    public CashContext(string type)
    {
        switch (type)
        {
            case "正常收费":
                CashNormal cs0 = new CashNormal();
                cs = cs0;
                break;
            case "满300返100":
                CashReturn cr1 = new CashReturn("300", "100");
                cs = cr1;
                break;
            case "打8折":
                CashRebate cr2 = new CashRebate("0.8");
                cs = cr2;
                break;
        }
    }

    public double GetResult(double money)
    {
        return cs.acceptCash(money);
    }

}

namespace 商场管理软件
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        double total = 0.0d;

        private void btnOk_Click(object sender, EventArgs e)
        {
            //利用简单工厂模式根据下拉选择框生成相应的对象，
            CashContext csuper = new CashContext(cbxType.SelectedItem.ToString());

            //通过多态可以得到收取费用的结果，
            double totalPrices = 0d;
            totalPrices = csuper.GetResult(Convert.ToDouble(txtPrice.Text) * Convert.ToDouble(txtNum.Text));
            total = total + totalPrices;
            lbxList.Items.Add("单价：" + txtPrice.Text + " 数量：" + txtNum.Text + " "
                + cbxType.SelectedItem + " 总计：" + totalPrices.ToString());
            lblResult.Text = total.ToString();
        }

        private void btnClear_Click(object sender, EventArgs e)
        {
            total = 0d;
            txtPrice.Text = "0.00";
            txtNum.Text = "0";
            lbxList.Items.Clear();
            lblResult.Text = "0.00";
        }

    }
}

2.7 策略模式分析

策略模式是一种定义一系列算法的方法，从概念上来看，所有这些算法完成的都是相同的工作，只是实现不同，它可以以相同的方式调用所有的算法，减少了各种算法类与使用算法类之间的耦合，

策略模式的Strategy类层次为Context定义了一系列的可供重用的算法或行为，继承有助于析取出这些算法中的公共功能，

策略模式的优点是简化了单元测试，因为每个算法都有自己的类，可以通过自己的接口单独测试，

策略模式就是用来封装算法的，在实践中可以用它来封装几乎任何类型的规则，只要在分析过程中听到需要在不同时间应用不同的业务规则，就可以考虑使用策略模式处理这种变化的可能性，