析构函数

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

1. 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。
2. 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。
3. 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！