3月 20 2015

strategy designpattern

#include <string>
#include <iostream>
#include <assert.h>
using namespace std;
class SaleStrategy
{
public:
    virtual float calculate(float price, int amount) = 0;
};
class RegularSaleStrategy : public SaleStrategy
{
public:
    virtual float calculate(float price, int amount)
    {
        return price * amount;
    }
};
class StudentSaleStrategy : public SaleStrategy
{
public:
    virtual float calculate(float price, int amount)
    {
        const float DISCOUNT = 0.5f;    //学生半价
 
        return (1-DISCOUNT) * price * amount;
    }
};
 
class BulkSaleStrategy : public SaleStrategy
{
public:
    virtual float calculate(float price, int amount)
    {
        const float DISCOUNT = 0.3f;    //批发折扣
        const int BULK_LIMIT = 100;     //>=100件按批发价
 
        if (amount >= BULK_LIMIT)
            return (1-DISCOUNT) * price * amount;
        return price * amount;
    }
};
class SaleManager
{
public:
    SaleManager(SaleStrategy* pSaleStrategy = NULL) : m_pSaleStrategy(pSaleStrategy) {}
 
public:
    void setStrategy(SaleStrategy* pSaleStrategy)
    {
        m_pSaleStrategy = pSaleStrategy;
    }
 
    float calculateTotal(float price, int amount)
    {
        assert(m_pSaleStrategy != NULL);
        float calResult = m_pSaleStrategy->calculate(price, amount);
        cout << "total price is: " << calResult << endl;
        return calResult;
    }
 
private:
    SaleStrategy* m_pSaleStrategy;
};
int main(int argc, char** argv)
{
    SaleStrategy* pSaleStrategy = new RegularSaleStrategy();
    SaleStrategy* pStudentSaleStrategy = new StudentSaleStrategy();
    SaleStrategy* pBulkSaleStrategy = new BulkSaleStrategy();
 
    SaleManager saleManager(pSaleStrategy);
    cout << "Regular Sale Strategy:\n"; 
    saleManager.calculateTotal(2.5f, 100);
 
    saleManager.setStrategy(pStudentSaleStrategy);
    cout << "Student Sale Strategy:\n";
    saleManager.calculateTotal(2.5f, 100);
 
    saleManager.setStrategy(pBulkSaleStrategy);
    cout << "Bulk Sale Strategy:\n";
    saleManager.calculateTotal(2.5f, 100);
 
    delete pBulkSaleStrategy;
    delete pStudentSaleStrategy;
    delete pSaleStrategy;
 
    return 0;
}