Basket

购物程序.png
//购物程序。主要知识点,面向对象设计中的继承和动态绑定!
//

#include "stdafx.h"
#include<fstream>
#include<sstream>
#include<string>
#include<memory>
#include<vector>
#include<iostream>
#include<set>

using namespace std;

class Book          //基类,包含销售价格和数量,以及书名等共有属性!
{
public:
    Book() = default;
    Book(const string &i,double p): id(i),sales_price(p) {};//只能可以 const string &s="abc"

    virtual double total_price(const unsigned &sales_count) { return sales_price*sales_count; }
    string get_name() const { return id; }
    double get_price() const { return sales_price; }
    
    virtual Book* clone() const & { return new Book(*this); }//借助clone函数,在创建对象时可以避免使用make_shared<Count_Quote>(),而直接使用Count_Quote cq()形式,容器在添加时使用vector.pushback(cq.clone())(将cq绑定到基类指针,添加至容器时更会发生动态绑定!)
       // virtual Quote* clone() && {return new Quote(std::move(*this));} 右值引用限定符&&,指明this是一个左值还是右值?右值引用应用的场景:返回非引用类型的函数,产生右值的表达式(算术表达式、关系表达式、位、后置递增递减)!(右值引用只能绑定到临时对象,接管资源,节省计算资源!)

    virtual ~Book() = default;
    //virtual string get_name() = 0;    顶层函数不能为抽象基类!
protected:
    double sales_price=0.0;
    //unsigned storage = 0;         库存量数据!
private:
    string id;      //id其派生类不需要访问!
};

class Quote :public Book        //抽象基类,包含打折信息!无法创建抽象基类对象!
{
public:
    Quote() = default;
    Quote(const string &i, double p, size_t q=0,double d=0,double m=0,double s=0) :Book(i, p), quantity(q),discount(d),minsales(m),sales(s) {};
    virtual double total_price(const unsigned &sales_count) = 0;

protected:
    size_t quantity = 0;
    double discount = 0.0;

    double minsales = 0.0;
    double sales = 0.0;

private:

};


class Price_Quote :public Quote     //满多少减多少
{
public://class默认是私有的!当自定义类发生错误时,可以通过创建类对象查找错误!
    Price_Quote() = default;
    Price_Quote(const string &i, double p, size_t q = 0, double d = 0, double m = 0, double s = 0) :Quote(i, p, q, d, m, s) {};
    double total_price(const unsigned &sales_count) override;
    Price_Quote *clone() const & { return new Price_Quote(*this); } //虚函数的返回类型可以为Price_Quote* !
};
double Price_Quote::total_price(const unsigned &sales_count)
{
    double ret = sales_price*sales_count;
    if (ret >= minsales && sales != 0)      //折扣不为0
    {
        int tmp = static_cast<int>(ret);
        ret = ret - (tmp / 100) * sales;        //每满100减5元!
        return ret;
    }
    else
    {
        return ret;
    }
}

class Count_Quote :public Quote //超过多少本,几折优惠?
{
public:
    Count_Quote() = default;
    Count_Quote(const string &i, double p, size_t q=0, double d=0, double m=0, double s=0) :Quote(i, p,q,d,m,s) {};
    double total_price(const unsigned &sales_count) override;//覆盖虚函数,overrid,final
    Count_Quote* clone() const & { return new Count_Quote(*this); }//不懂!
};
double Count_Quote::total_price(const unsigned &sales_count)
{
    if (sales_count >= quantity && discount!=0)//折扣不为0
    {
        return sales_price*sales_count*discount;
    }
    else
    {
        return sales_price*sales_count;
    }
}


class Shop
{
public:
    //friend class Basket;友元表示可以访问保护和私有成员,但是访问的方式依旧是Shop.item()
    Shop() = default;
    Shop(const string &s) {read_file(s); }

    explicit operator bool() const { return item.size() > 0 ? true : false; }   //自定义类型转换!充当判断条件使用!
    void operator()(string s = "\n") { cout << item.size() << s; }              //函数调用运算符!

    void init(const string &s)  //初始化商店!(重新加载商品信息!)
    {
        item = set<shared_ptr<Book>>();
        read_file(s);
    }
    shared_ptr<Book> find_s(const string &s)        //查找商品
    {
        for (auto &r : item)
        {
            if (s == r->get_name())
            {
                return r;
            }
        }
        return nullptr;
    }

    
private:
    set<shared_ptr<Book>> item;//
    void read_file(const string &filename);
};

void Shop::read_file(const string &filename)
{
    ifstream rd_file(filename);
    if (rd_file)
    {
        string tmp;
        string id;              //书名,书名可能含有空格,如何剥离出书名?
        double p=0;             //售价
        size_t q = 0;           //打折起始数量
        double d = 0;           //折扣?
        double m = 0;           //满m减
        double s = 0;           //满m减多少元?
        unsigned tag = 1;       //打折方式,1为数量,2为总价

        getline(rd_file, tmp);  //去掉首行介绍信息! 
        while (getline(rd_file,tmp))
        {
            istringstream rd_info(tmp);
            rd_info >> id >> p >> q >> d >> m >> s>>tag;
            if (tag == 1)
            {
                item.insert(make_shared<Count_Quote>(id, p, q, d, 0, 0));
            }
            if (tag == 2)
            {
                item.insert(make_shared<Price_Quote>(id, p, 0, 0, m, s));
            }
        }
        rd_file.close();
    }
}

class Basket
{
public:
    Basket(Shop shop):sp(make_shared<Shop>(shop)){}
    void buy_s(const string &s);

    friend ostream& operator<<(ostream &os,const Basket &bst);

private:
    static bool compare(const shared_ptr<Book> &lh, const shared_ptr<Book> &rh) { return lh->get_name() < rh->get_name(); }//必须为常量引用,可以引用常量和非常量!

    multiset<shared_ptr<Book>, decltype(compare)*> buy{compare};    //自定义排序方法//为什么不用vector?compare的返回值必须是static bool
    shared_ptr<Shop> sp;
};

void Basket::buy_s(const string &s)
{
    if (sp->find_s(s) != nullptr)
    {
        buy.insert(sp->find_s(s));
    }
}

ostream& operator<<(ostream &os,const Basket &bst)
{
    double sum = 0;
    for (auto beg = bst.buy.cbegin(); beg != bst.buy.cend(); beg = bst.buy.upper_bound(*beg))
    {
        auto sales_count = bst.buy.count(*beg);
        sum = sum + (*beg)->total_price(sales_count);
        //Basket::print();非静态成员引用必须与对象相对!
        os << "BookName: " << (*beg)->get_name() << " \t " << (*beg)->get_price() << " \t " << sales_count << " \t " << (*beg)->total_price(sales_count) << endl;
    }
    os << "Total price: " << sum << endl;
    return os;
}

int main()
{
    
    Price_Quote pq("c++", 99, 2, 8, 100, 5);
    Count_Quote cq("c++", 99, 2, 8, 100, 5);

    vector<shared_ptr<Book>> vbook;
    auto tmp1 = shared_ptr<Book>(pq.clone());//借助虚函数clone,智能指针可以均为Book模版!
    auto tmp2 = shared_ptr<Book>(cq.clone());
    vbook.push_back(tmp1);
    vbook.push_back(tmp2);


    Shop sp;
    sp.init("C:\\Users\\winack\\Documents\\Visual Studio 2017\\Projects\\BookStore\\123.txt");

    sp("-goods!");      //类的函数调用运算符,可以像函数一样使用类对象!

    if (sp)     //如果sp读取了商品信息!
    {
        Basket bt(sp);
        bt.buy_s("C++Primer");
        bt.buy_s("Thelovestreng");
        bt.buy_s("Hackcook");
        bt.buy_s("Hackcook");
        bt.buy_s("C++Primer");
        cout << bt;
    }

    system("pause");
    return 0;
}

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