C++基础——类封装简单示例

 1 #ifndef STOCK00_H_
 2 #define STOCK00_H_
 3 
 4 #include <string>
 5 
 6 class Stock
 7 {
 8 private:
 9     std::string m_company;
10     long m_shares;
11     double m_share_val;
12     double m_total_val;
13     void set_tot() {m_total_val = m_shares * m_share_val;}//内联函数
14 public:
15     //two constructors
16     Stock();//default constructor
17     Stock(const std::string &co,long n = 0,double pr = 0.0);
18     //destructor
19     ~Stock();
20     void acquire(const std::string &co,long n,double pr);
21     void buy(long num,double price);
22     void sell(long num,double price);
23     void update(double price);
24     void show() const;//promises not to change invoking object
25     const Stock &topval(const Stock &s) const;
26 };
27 
28 #endif

#include <iostream>
#include "stock00.h"

Stock::Stock()
{
    std::cout << "Default constructor called.\n";
    m_company = "no name";
    m_shares = 0;
    m_share_val = 0.0;
    m_total_val = 0.0;
}

Stock::Stock(const std::string &co,long n,double pr)
{
    std::cout << "Constructor using " << co << " called\n";
    m_company = co;

    if(n<0)
    {
        std::cout <<"Number of shares can't be negative;"
            << m_company << "shares set to 0.\n";
        m_shares = 0;
    }
    else
        m_shares = n;
    m_share_val = pr;
    set_tot();
}

Stock::~Stock()
{
    std::cout << "Bye, " << m_company << "!\n";
}

void Stock::acquire(const std::string &co,long n,double pr)
{
    m_company = co;
    if(n<0)
    {
        std::cout << "Number of shares can't be negative; "
                  << m_company << "shares set to 0.\n";
        m_shares = 0;
    }
    else
        m_shares = n;
    m_share_val = pr;
    set_tot();
}

void Stock::buy(long num, double price)
{
    if(num<0)
    {
        std::cout << "Number of shares purchased can't be negative."
                   << "Transcation is aborted.\n";
    }
    else
    {
        m_shares += num;
        m_share_val = price;
        set_tot();
    }
}

void Stock::sell(long num,double price)
{
    using std::cout;
    if(num < 0)
    {
        cout << "Number of shares sold can't be negative. "
             << "Transcation is aborted.\n";
    }
    else if(num > m_shares)
    {
        cout <<"You can't sell more than you have! "
             << "Transcation is aborted.\n";
    }
    else 
    {
        m_shares -=num;
        m_share_val = price;
        set_tot();
    }
}

void Stock::update(double price)
{
    m_share_val = price;
    set_tot();
}

void Stock::show() const
{
    std::cout << "Company: " << m_company << " Shares:  " << m_shares << '\n'
              << "share Price:$" << m_share_val << " total worth:$" << m_total_val<< std::endl;
}
//选择总价最高的股票，返回该股票
const Stock & Stock::topval(const Stock &s) const
{
    if(s.m_total_val > m_total_val)
        return s;
    else
        return *this;
}

 1 #include <iostream>
 2 #include "stock00.h"
 3 
 4 const int STKS = 4;
 5 int main()
 6 {
 7     Stock stocks[STKS] = {//create object array of Stock class
 8         Stock("NanoSmart",12,20.0),
 9         Stock("Boffo Objects",200,2.0),
10         Stock("Monolithic Obelisks",130,3.25),
11         Stock("Fleep Enterprises",60,6.5)
12     };
13 
14     std::cout << "Stock holdings:\n";
15     int st;
16     for (st=0;st<STKS;st++)
17     {
18         stocks[st].show();//show informations
19     }
20 
21     //set top pointer to the first element
22     const Stock *top = &stocks[0];
23     for(st=1;st<STKS;st++)
24     {
25         top = &top ->topval(stocks[st]);
26     }
27     //now top points to the most valuable holding
28     std::cout <<"\nMost valuable holding:\n";
29     top->show();
30     return 0;
31 }