析构函数

用构造函数创建对象后，程序负责跟踪该对象，直到其过期为止。

对象过期时，程序将自动调用一个特殊的成员函数——析构函数来完成清理工作。

析构函数的声明

~Share();

析构函数的定义

Share::~Share() { cout << "ByeBye!!!" << company << endl; }

析构函数的调用

析构函数的调用是由编译器决定的，通常不应该在代码中显示地调用析构函数

如果创建的是静态存储类对象，则其析构函数将在程序结束时自动被调用。如果创建的是自动存储类对象，则其析构函数将在程序执行完代码块时自动被调用。如果对象是通过new创建的，则它将驻留在栈内存或自由存储中，当使用delete来释放内存时，其析构函数将自动被调用。

改进的Share类

类的声明

// // Created by Administrator on 2017/3/7. // #ifndef PROJECT1_SHARE_H #define PROJECT1_SHARE_H #include <array> using namespace std; class Share { private: string company; long shares; double share_value; double total_value; void set_total(){ total_value = shares * share_value; } public: Share();//默认构造函数 Share(const string &comp , long number , double price);//构造函数 ~Share();//析构函数 void buy(long number , double price); void sell(long number , double price); void update(double price); void show(); }; #endif //PROJECT1_SHARE_H

类的定义

// // Created by Administrator on 2017/3/7. // #include <iostream> #include "Share.h" Share::Share(const string &comp, long number, double price) { company = comp; if (number < 0){ cout << "The number of shares purchased can not be less than zero, the transaction canceled!" << endl; shares = 0; } else shares = number; share_value = price; set_total(); } Share::Share() { } Share::~Share() { cout << "ByeBye!!!" << company << endl; } void Share::buy(long number, double price) { if (number < 0){ cout << "The number of shares purchased can not be less than zero, the transaction canceled!" << endl; } else{ shares += number; share_value = price; set_total(); } } void Share::sell(long number, double price) { if (number < 0){ cout << "The number of shares sold can not be less than zero, the transaction canceled!" << endl; } else if (number > shares){ cout << "The number of shares sold can not be greater than the number of existing shares, the transaction canceled!" << endl; } else{ shares -= number; share_value = price; set_total(); } } void Share::update(double price) { share_value = price; set_total(); } void Share::show() { cout << "Company Name: " << company << endl; cout << "Number of shares held:" << shares << endl; cout << "Stock price:" << share_value << endl; cout << "Total stock:" << total_value << endl; }

类的使用

#include <iostream> #include <string> #include "cmake-build-debug/Share.h" using namespace std; int main() { cout << "Using constructors to create new object : " << endl; Share xiong1("alibabab" , 1000 , 18.88); xiong1.show(); Share xiong2 = Share("LENOVO" , 1000 , 9.88); xiong2.show(); cout << "Assigning xiong1 to xiong2 : " << endl; xiong2 = xiong1; xiong1.show(); xiong2.show(); cout << "Using constructors to reset an object : " << endl; xiong1 = Share("JD" , 10000 , 6.4); xiong1.show(); return 0; }

测试结果

H:\Project1\cmake-build-debug\Project1.exe Using constructors to create new object : Company Name: alibabab Number of shares held:1000 Stock price:18.88 Total stock:18880 Company Name: LENOVO Number of shares held:1000 Stock price:9.88 Total stock:9880 Assigning xiong1 to xiong2 : Company Name: alibabab Number of shares held:1000 Stock price:18.88 Total stock:18880 Company Name: alibabab Number of shares held:1000 Stock price:18.88 Total stock:18880 Using constructors to reset an object : ByeBye!!!JD Company Name: JD Number of shares held:10000 Stock price:6.4 Total stock:64000 ByeBye!!!alibabab ByeBye!!!JD Process finished with exit code 0

从中我们可以看出析构函数调用的一些规则！