C++类的使用出现的问题

Question

为什么这个函数里面使用不了这个类里面的变量，使用这个m_Empnum的时候就提示this是空指针，下面用到类里面的m_EmpArray也是出现同样的错误。

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

doWork::doWork() {
    m_Empnum = 0;
    m_EmpArray = NULL;
}

doWork::~doWork() {
    if (m_EmpArray != NULL) {
        delete[] m_EmpArray;
        m_EmpArray = NULL;
    }
}

void doWork::showmenu() {
    cout << "****************************************" << endl;
    cout << "*********欢迎使用职工管理系统 **********" << endl;
    cout << "************0、退出管理程序*************" << endl;
    cout << "************1、增加员工信息*************" << endl;
    cout << "************2、显示职工信息*************" << endl;
    cout << "************3、删除离职职工*************" << endl;
    cout << "************4、修改职工信息*************" << endl;
    cout << "************5、查找职工信息*************" << endl;
    cout << "************6、按照编号排序*************" << endl;
    cout << "************7、清空所有文档*************" << endl;
    cout << "****************************************" << endl;
}

void doWork::exitSystem() {
    cout << "欢迎下次使用。" << endl;
    exit(0);
}

void doWork::Add_Sys() {
    int addnum = 0;
    int i;
    int id;
    string name;
    int depselect;
    cout << "请输入添加的人数：" << endl;
    cin >> addnum;
    if (addnum > 0) {
        int k = addnum + this->m_Empnum;
        worker** newspace = new worker * [k+4];
        //newspace = new worker * [k];
        if (m_Empnum != 0) {
            for (i = 0; i < m_Empnum; i++) {
                newspace[i] = m_EmpArray[i];
            }
            for (; i < m_Empnum + addnum; i++) {
                cout << "请输入员工编号：" << endl;
                cin >> id;
                cout << "请输入员工姓名：" << endl;
                cin >> name;
                cout << "请输入员工岗位编号：" << endl;
                cout << "1、普通员工" << endl
                    << "2、经理" << endl
                    << "3、老板" << endl;
                cin >> depselect;
                worker* worker = NULL;
                switch (depselect) {
                case 1:worker = new employee(id, name, depselect);
                    break;
                case 2:worker = new manager(id, name, depselect);
                    break;
                case 3:worker = new boss(id, name, depselect);
                    break;
                default:
                    break;
                }
                newspace[i] = worker;
            }
            m_Empnum += addnum;
            delete[] m_EmpArray;
            m_EmpArray = newspace;
            cout << "成功添加" << addnum << "名新员工。" << endl;
        }
        else cout << "添加有错。" << endl;
        system("cls");
    }
}

Answer 1

你把调用的代码和类的声明也发一下