设计模式：Strategy(策略)

TaxStrategy.h

#pragma once
class TaxStrategy
{
    virtual double Calculate() = 0;
    virtual ~TaxStrategy() {};
};

CNTax.h

#pragma once
#include "TaxStrategy.h"
class CNTax :
    public TaxStrategy
{
public:
    virtual double Calculate();
};

DETax.h

#pragma once
#include "TaxStrategy.h"
class DETax :
    public TaxStrategy
{
    virtual double Calculate();
};

USTax.h

#pragma once
#include "TaxStrategy.h"
class USTax :
    public TaxStrategy
{
public:
    virtual double Calculate();
};

SalesOrder.h

#pragma once
#include"TaxStrategy.h"
class SalesOrder
{
    TaxStrategy * strategy;
public:
    SalesOrder(StrategeFactory * factory);//需要一个工厂类，省略
    ~SalesOrder();
    double Calculate();
};

TasStrategy.cpp

#include "TaxStrategy.h"

CNTax.cpp

#include "CNTax.h"

double CNTax::Calculate()
{
    return 111.111;
}

DETax.cpp

#include "DETax.h"

double DETax::Calculate()
{
    return 333.333;
}

USTax.cpp

#include "USTax.h"

double USTax::Calculate()
{
    return 222.222;
}

SalesOrder.cpp

#include "SalesOrder.h"

SalesOrder::SalesOrder(StrategeFactory * factory)
{
    this->strategy = StrategyFactory->newStrategy();
}

SalesOrder::~SalesOrder()
{
    delete this->strategy;
}

double SalesOrder::Calculate()
{
    double val = strategy->Calculate();
    return val;
}

main.cpp

#include <iostream>
#include"SalesOrder.h"
int main()
{
    std::cout << "Hello World!\n";
}