C++中构造函数与析构函数的详解及其作用介绍

Class::Class(); // 构造函数

class Time {
private:
    int hour;
    int minute;
    int second;
public:
    Time(); // 默认构造函数
    void set_time(int h, int m, int s);
    void show_time();
};

#include "Time.h"
#include <iOStream>

using namespace std;

Time::Time() {
    hour = 0;
    minute = 0;
    second = 0;
}

void Time::set_time(int h, int m, int s) {
    hour = h;
    minute = m;
    second = s;
}

void Time::show_time() {
    cout << hour << ":" << minute << ":" << second << endl;
}

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

using namespace std;

int main() {

    Time time1;  // 实例化time
    time1.show_time();  // 调用show_time

    return 0;
}

#ifndef PROJECT1_TIME_H
#define PROJECT1_TIME_H

class Time {
private:
    int hour;
    int minute;
    int second;
public:
    Time();  // 默认构造函数
    Time(int h, int m=0, int s=0);  // 有参构造函数
    void show_time();
};

#endif //PROJECT1_TIME_H

#include "Time.h"
#include <iostream>
using namespace std;

// 默认构造函数
Time::Time() : hour(0), minute(0), second(0) {}

// 有参构造函数
Time::Time(int h, int m, int s) : hour(h), minute(m), second(s) {}


void Time::show_time() {
    cout << hour << ":" << minute << ":" << second << endl;
}

#include "Time.h"
#include <iostream>
using namespace std;

int main() {

    Time time1;
    time1.show_time();

    Time time2(8);
    time2.show_time();

    Time time3(8, 8);
    time3.show_time();
    
    Time time4(8, 8, 8);
    time4.show_time();

    return 0;
}

Class::~Class();  // 析构函数

#ifndef PROJECT1_STUDENT_H
#define PROJECT1_STUDENT_H

#include <string>
using namespace std;

class Student {
private:
    int num;
    string name;
    char gender;
public:
    Student();
    Student(int num, string name, char gender);
    ~Student();
    void display();
};

#endif //PROJECT1_STUDENT_H

#include "Student.h"
#include <iostream>
using namespace std;

// 无参构造
Student::Student() : num(-1), name("None"), gender('N') {}

Student::Student(int n, string p, char g) : num(n), name(p), gender(g) {
    cout << "执行构造函数: " << "Welcome, " << name << endl;
}

void Student::display() {
    cout << "num: " << num << endl;
    cout << "name: " << name << endl;
    cout << "gender: " << gender << endl;
    cout << "===============" << endl;
}

Student::~Student() {
    cout << "执行析构函数: " << "Bye bye, " << name << endl;
}

#include "Student.h"
#include <iostream>
using namespace std;

int main() {

    Student student1(1, "Little white", 'f');
    Student student2(2, "Big white", 'f');

    student1.display();
    student2.display();

    return 0;
}