C++ 类的抽象初练

/*
某商店经销一种货物，货物的购进和卖出以箱为单位，各箱的重量不一样，
因此商店需要目前库存的总重量。
现在用c++模拟商店货物购进和卖出的情况

*/

#include<iostream>
using namespace std;


//货物类
class Goods{
public:
    Goods(int w=0){
        this->weight = w;
    }
    int GetW(){
        return weight;
    }
    Goods *next;
private:
    //重量
    int weight;
};

//商店类
class Shop{
public:
    Shop(int s=0){
        this->weights = s;
        pHead = NULL;
    }
    ~Shop(){
        if (pHead!=NULL)
        {
            Goods *pCurrent = pHead;
            Goods *pNext = NULL;
            while (pCurrent){
                pNext = pCurrent->next;
                delete pCurrent;
                pCurrent = NULL;
                pCurrent = pNext;
            }
        }
        weights = 0;
    }
    //卖出
    void SellOut(){
        if (pHead==NULL)
        {
            cout << "商店里已经没有货物了！" << endl;
        }
        else{
            //队列  先进先出
            Goods *pCurrent = pHead;
            pHead = pHead->next;
            delete pCurrent;
        }
    }
    //购进
    void Purchase(Goods *&pin){
        if (pHead==NULL)
        {
            //插入第一箱货物
            pHead = pin;
            weights += pin->GetW();
        }
        else{
            Goods *pCurrent = pHead;
            while (pCurrent->next){
                pCurrent = pCurrent->next;
            }
            pCurrent->next = pin;
            weights += pin->GetW();
        }
    }
    //查询货物重量
    int GetWeight(){
        return weights;
    }
private:
    int weights;
    Goods *pHead;
};

void protectA(){
    Shop *sp = new Shop();
    int indexover = 1;
    while (indexover){
        int num = 0;
        int w = 0;
        cout << "请输入操作：" << endl;
        cout << "1购进货物" << endl;
        cout << "2卖出货物" << endl;
        cout << "3查看现有货物重量" << endl;
        cout << "按任意键退出" << endl;
        cin >> num;
        switch (num)
        {
        case 1:
            cout << "请输入货物的重量" << endl;
            //备注：在c++中不可以在case语句里定义任意变量,如果非要定义，请外面套上大括号{}
            //int ss = 0;
            //报错 ： error C2360: “ss”的初始化操作由“case”标签跳过
            {
                cin >> w;
                Goods * g1 = new Goods(w);
                sp->Purchase(g1);
            }
            break;
        case 2:
            {
                sp->SellOut();
            }
            break;
        case 3:
            cout << "现有货物的重量是" << sp->GetWeight() << endl;
            break;
        default:
            indexover = 0;
            break;
        }
    }
    if (sp!=NULL)
    {
        delete sp;
    }
}
void main(){
    protectA();
    system("pause");
}