策略模式

1】什么是策略模式？

坊间的解释都比较拗口，而且不好理解。

所谓策略模式，先构建一个策略(即子类的实例)，再利用这个具体的实例构建一个策略对象，通过调用策略对象的接口可以达到相应具体策略的结果。

【2】策略模式代码示例

代码示例：
/*
  * 策略模式
  */

#include <iostream>
#include <cmath>
#include <string>
using namespace std;

class CashSuper
{
public:
    virtual double acceptMoney(double money) = 0;
};

class CashNormal : public CashSuper
{
public:
    double acceptMoney(double money)
    {
        return money;
    }
};

class CashRebate : public CashSuper
{
private:
    double discount;

public:
    CashRebate(double dis)
    {
        discount = dis;
    }
    double acceptMoney(double money)
    {
        return money * discount;
    }
};


class CashReturn : public CashSuper
{
private:
    double moneyCondition;
    double moneyReturn;

public:
    CashReturn(double mc, double mr)
    {
        moneyCondition = mc;
        moneyReturn = mr;
    }
    double acceptMoney(double money)
    {
        double result = money;
        if (money >= moneyCondition)
        {
            result = money - floor(money / moneyCondition) * moneyReturn;
        }
        return result;
    }
};

class  CashContext
{
private:
    CashSuper *cs;
public:
    CashContext(CashSuper *cs)
    {
        this->cs = cs;
    }
    double getResult(double money)
    {
        return cs->acceptMoney(money);
    }
};

void main()
{
    CashSuper *cs;
    CashContext *cc;
    double money = 1000;

    cs = new CashRebate(0.8);
    cc = new CashContext(cs);
    cout << cc->getResult(money) << endl;

    money = 1000;
    cs = new CashNormal();
    cc = new CashContext(cs);
    cout << cc->getResult(money) << endl;

}

【3】策略与工厂结合模式代码示例
/*
  * 策略与工厂模式
  */
#include <iostream>
#include <cmath>
#include <string>
using namespace std;

class CashSuper
{
public:
    virtual double acceptMoney(double money) = 0;
};

class CashNormal : public CashSuper
{
public:
    double acceptMoney(double money)
    {
        return money;
    }
};

class CashRebate : public CashSuper
{
private:
    double discount;
public:
    CashRebate(double dis)
    {
        discount = dis;
    }
    double acceptMoney(double money)
    {
        return money * discount;
    }
};


class CashReturn : public CashSuper
{
private:
    double moneyCondition;
    double moneyReturn;
public:
    CashReturn(double mc, double mr)
    {
        moneyCondition = mc;
        moneyReturn = mr;
    }
    double acceptMoney(double money)
    {
        double result = money;
        if (money >= moneyCondition)
        {
            result = money - floor(money / moneyCondition) * moneyReturn;
        }
        return result;
    }
};

class  CashContext
{
private:
    CashSuper *cs;
public:
    CashContext(string str)
    {
        if ("正常收费" == str)
        {
            cs = new CashNormal();
        }
        else if ("打9折" == str)
        {
            cs = new CashRebate(0.9);
        }
        else if ("满300送200" == str)
        {
            cs = new CashReturn(300, 200);
        }        
    }
    double getResult(double money)
    {
        return cs->acceptMoney(money);
    }
};


int main()
{
    double money = 1000;
    CashContext *cc = new CashContext("打9折");
    cout << cc->getResult(money);
    return 0;
}

http://www.cnblogs.com/Braveliu/p/3938368.html