c++ 析构函数

1析构函数.

#include<iostream>
#include <stdlib.h>
#include <string.h>
using namespace std;
struct Student{
    int id=1001;//成员变量或对象
    char *name=nullptr;
    int age=20;
    int score=99;
    Student(){cout<<"student default construction!"<<endl;}
    Student(int i,const char*n, int a,int s){
        id=i;
        if(n){
            name =(char*)malloc(strlen(n)+1);
            strcpy(name,n);
        }
        age=a;score=s;
    }

    //析构函数是释放初始化的变量(在构造函数里做过内存申请的)
    //析构函数不可以重载
    ~Student()
    {
        cout<<"called destructor!"<<endl;
        if(name)free(name);
    }

};//end class Student

int main()
{
    Student stu1(1002,"lisi",20,90);
//  Student *pstu1 = new Student();
    cout<<stu1.name<<endl;
    return 0;
}

2 构造和析构的顺序

#include<iostream>
#include <stdlib.h>
#include <string.h>
using namespace std;
struct Student{
    int id=1001;//成员变量或对象
    char *name=nullptr;
    int age=20;
    int score=99;
    Student(){cout<<"student default construction!"<<endl;}
    Student(int i,const char*n, int a,int s){
    cout<<"student "<<n<<" construction!"<<endl;
        id=i;
        if(n){
            name =(char*)malloc(strlen(n)+1);
            strcpy(name,n);
        }
        age=a;score=s;
    }
    //析构函数是释放初始化的变量
    //析构函数不可以重载
    ~Student()
    {
        cout<<"student "<<name<<" destructor!"<<endl;
        if(name)free(name);
    }

};//end class Student

int main()
{
    Student stu1(1002,"lisi",20,90);
    Student stu2(1003,"maliu",20,90);
//  cout<<stu1.name<<endl;
    return 0;
}

3 类类型成员的构造和析构

#include<iostream>
#include <stdlib.h>
#include <string.h>
using namespace std;
struct book_bag{
    int color;
    int book_sum;
    book_bag(){
        cout<<"book default constrcution!"<<endl;
    }
    book_bag(int c, int b){
        cout<<"book constrcution!"<<endl;
        color =c,book_sum = b;
    }
    ~book_bag(){
        cout<<"book destrcutor!"<<endl;
    }
};
struct Student{
    int id=1001;//成员变量或对象
    char *name=nullptr;
    int age=20;
    int score=99;
    book_bag bg;

    Student(){cout<<"student default construction!"<<endl;}
    Student(int i,const char*n, int a,int s){
    cout<<"student "<<n<<" construction!"<<endl;
        id=i;
        if(n){
            name =(char*)malloc(strlen(n)+1);
            strcpy(name,n);
        }
        age=a;score=s;
    }
    //析构函数是释放初始化的变量
    //析构函数不可以重载
    ~Student()
    {
        cout<<"student "<<name<<" destructor!"<<endl;
        if(name)free(name);
    }

};//end class Student

int main()
{
    Student stu1(1002,"lisi",20,90);
    Student stu2(1003,"maliu",20,90);
//  cout<<stu1.name<<endl;
    return 0;
}