构造函数和析构函数

Stock(const string &co,long n = 0,double pr  0.0);
//定义可以这样写
Stock::Stock(const string &co,long n,double pr)
{
    company = co;
    if (n < 0)
    {
        std::cout << "Number of shares can't be negative;"
            << "company " << "share set to 0.\n";
        share = 0;
    }
    else
    {
        share = n;
        share_val = pr;
        set_tot();
    }
}

class Stock
{
private:
string m_commpany;
long m_shares;
}

Stock::Stock();

Stock s1;//这种调用默认构造函数将会出错

Stock::Stock()
{
commpany = "no name";
share = 0;
share_val = 0.0;
total_val = 0.0;
}

Stock::~Stock();

//stock.h
#pragma once
#include<string>
#ifndef  _STOCK_H
#define _STOCK_H
class Stock
{
private:

 std::string company;
 long share;
 double share_val;
 double total_val;
 void set_tot() { total_val = share_val * share; }
public:
 Stock();
 ~Stock();
 Stock(const std::string& co, long n, double pr);
 void buy(long num, double price);
 void sell(long num, double price);
 void update(double price);
 void show();
};
#endif // ! _STOCK_H

//stcok.cpp
#include<iostream>
#include"stcok.h"
Stock::Stock()
{
 std::cout << "Default cibstructor called\n";
 company = "no name";
 share = 0;
 share_val = 0.0;
 total_val = 0.0;
}
 Stock::Stock(const std::string& co, long n, double pr)
{
 std::cout << "Constructor using " << co << " called\n";
 company = co;
 if (n < 0)
 {
     std::cout << "Number of shares can't be negative;"
         << "company " << "share set to 0.\n";
     share = 0;
 }
 else
 {
     share = n;
     share_val = pr;
     set_tot();
 }
}
 Stock::~Stock()
 {
  std::cout << "bye, " << company << "!\n";

 }
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
 {
     share += num;
     share_val = price;
     set_tot();
 }
}
void Stock::sell(long num, double price)
{
 using std::cout;
 if (num < 0)
 {
     cout << "Number if shares sold can't be negative. "
         << "Transcation is aborted.\n";
 }
 else if (num>share)
 {
     cout << "You can't sell more than you have"
         << "Transcation is aborted.\n";
 }
 else
 {
     share -= num;
     share_val = price;
     set_tot();
 }
}
void Stock::update(double price)
{
 share_val = price;
 set_tot();
}
void Stock::show()
{
 std::cout << "Company: " << company
     << "Share: " << share << '\n'
     << "share price: $" << share_val
     << "Total Worth: $" << total_val << '\n';
}

//main.cpp
#include<iostream>
#include"stcok.h"
int main()
{
 using std::cout;
 cout << "Using constructors to create new objects\n";
 Stock s1("NanoSmart",12,20.0);
 s1.show();
 Stock s2 = Stock("Boffo Objects", 2, 2.0);
 s2.show();
 cout << "Assigning stock1 to stcok2:\n";
 //s1.buy(15, 18.125);
 //s1.show();
 s2 = s1;
 cout << "Listing stock1 and stock2:\n";
 s1.show();
 s2.show();
 cout << "Using a constructor to reset an object\n";

 s1 = Stock("Nifty Foods", 10, 50.0);
 cout << "Revised s1:\n";
 s1.show();
 cout << " Done\n";
 
 return 0;

}