[C++知识库]37_C++【不同实例化对象的地址】【类内公有静态成员属性】【类内公有静态成员函数】【常函数信息】【类外_const修饰的常对象】【内部静态函数给静态成员（公有、私有）赋值】

box.h

#ifndef BOX_H
#define BOX_H
#include<iostream>
#include<cstring>
#include<malloc.h>
using namespace std;

class Box
{
public:
    Box();
    Box(int a, int b, int c, char *name, char str);
    Box(const Box&p);
    void Surface_area();
    void box_v();
    void setval(int a, int b, int c, char *name, char str,int num2);
    void printf_name();
    void printf_str();
    void printf_val();
    ~Box();

    static void printf_str_1()//需要在main中由类对象引出打印！！
    {
        num = 10;
        num2 = 60;
        cout << "内部静态函数给静态成员（公有、私有）赋值" << endl;//?
        cout << num << endl;
        cout << num2 << endl;
    }

    void test00() const//常函数--仅可以查看类内的成员变量信息，想要修改成员变量，必须加mutable 才可以
    {
        m = 100;
        num = 111;
        num2 = 222;
        //x = 100;mutable未修饰x所以无法修改左值
        cout << "类内_mutable修饰 m= " << m << endl;
        cout << "类内_x= " << x << endl;
        cout << "类内_w= " << w << endl;
        cout << "类内_n= " << n << endl;
        cout << "类内_未被mutable修饰的静态公有静态成员：num= " << num << endl;
        cout << "类内_未被mutable修饰的静态私有静态成员：num2= " << num2 << endl;
        cout << "类内_name_1= " << name_1 << endl;// ?
        cout << "类内_h= " << h << endl;// ?
        //cout << "类内_str= " << str << endl;// ?
    }

    static int num;
    int n;
    mutable int m;//加上mutable常对象即可修改

private:
    int x;
    int w;
    int *h;
    char *name_1;
    char str;
    static int num2;
};

#endif // BOX_H

box.cpp

#include "box.h"

int Box::num = 10;
int Box::num2 = 20;
//static void Box::printf_str_1()！！类内的静态函数不可以放到外面

Box::Box()
{
    cout<<"默认构造！！！"<<endl;
    x = 0;
    w = 0;
    h = new int;
    str = NULL;
    name_1 = new char[40];
    n = 0;
}

Box::Box(int a, int b, int c, char *name, char str)
{
    cout<<"有参构造"<<endl;
    this->x = a;
    this->w = b;
    this->h = new int(c);
    this->str = str;

    this->name_1 = new char[40];
    strcpy(this->name_1, name);
}

Box::Box(const Box &p)
{
    this->x = p.x;
    this->h = new int (*p.h);
    this->w = p.w;
    this->str = p.str;

    this->name_1 = new char[20];
    strcpy(this->name_1, p.name_1);
}

void Box::Surface_area()
{
    int i = 2 * ((x * w ) + (w * (*h)) + (x * (*h)));
    cout<< "表面积是："<< i << endl;
}

void Box::box_v()
{
    int i = x * w * (*h) ;
    cout<< "该立方体的体积为："<< i << endl;
}

void Box::setval(int a, int b, int c, char *name, char str, int num2)
{
    this->x = a;
    this->w = b;
    this->h = new int(c);
    this->str = str;
    Box::num2 = num2;

    this->name_1 = new char[20];
    strcpy(this->name_1, name);
}

void Box::printf_name()
{
    cout << "长方体名称："<< name_1 << endl;
}

void Box::printf_str()
{
    cout << "长方体编号：" << str << endl;
}

void Box::printf_val()
{
    cout << (*h) <<" "<< w <<" "<< x <<" "<< name_1 <<" "<< str \
         << num2<< endl;
}


Box::~Box()
{
    cout<<"析构函数释放~"<< endl;
    if(h != NULL)
    {
        delete h;
    }
    if(name_1 != NULL)
    {
        delete[]name_1;
    }
}

main.cpp

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


int main()
{
   #if 0
    cout << "输出rec2的信息-赋值+打印：" << endl;
    Box rec;
    rec.setval(10, 5, 6,"box", 'a',223);
    cout << "地址：" << &rec << endl;
    rec.printf_val();


    cout << "输出rec2的信息-赋值+打印：" << endl;
    Box rec2;
    rec2.setval(1, 2, 3,"dd", 'c',23);//调用有参构造
    cout << "地址：" << &rec2 << endl;
    rec2.printf_val();
    putchar('\n');
   #endif

   #if 0
    cout << "类内公有静态成员属性-赋值+打印：" << endl;
    Box::num = 220;
    cout << Box::num << endl;
    putchar('\n');
   #endif

   #if 0
    cout << "类内公有静态成员函数-打印：" << endl;
    Box::printf_str_1();
    putchar('\n');
   #endif

   #if 1
    Box rec3;
    cout << "常函数信息：" << endl;
    rec3.test00();
    putchar('\n');
   #endif

   #if 0
    const Box rec4;
    cout << "类外_const修饰的常对象.赋值+打印：" << endl;
    rec4.m = 2;
    rec4.num = 333;
    //rec4.num2 = 10;//私有静态无法修改,num是公有静态可以
    cout << "m = " << rec4.m << endl;
    putchar('\n');
   #endif


    return 0;
}

图示：

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