字符指针，使用 cin.getline 读取？

Question

Currently doing some homework, and I got some issues. My program is crashing whenever I write in my char pointer firstname. I got char* firstname, and I try to use cin.getline(firstname, MAXTXT) where MAXTXT = 80; - This causes my program to crash, same happens to my char* lastname. I do suspect is has something to do with allocating memory? As it worked fine with my dob cin.getline.

How am I supposed to read input from user and into a char pointer? I have to use cin/cin.getline and not other kind of strings as that's a part of the homework. I can use whatever is in // after the includes.

#ifdef _MSC_VER
#define _CRT_SECURE_NO_WARNINGS
#endif 

//  INCLUDE:
#include  <iostream>         //  cin, cout
#include  <cstring>          //  strcpy, strlen, strncmp
#include  <cctype>           //  toupper
#include  <cstdlib>          //  itoa
#include <iomanip>           // setw

using namespace std;

//  CONST:
const int MAXEMP = 100;     //  Max. amount of employees.
const int MAXTXT = 80;     //  Max lenght for text/string.
const int DATELEN = 7;     //  Fixed lenght for date incl \0.

                           //  ENUM:
enum Gender { female, male };

//  FUNCTION DECLARATION
void printMenu();
char read();
int  read(const char* t, int min, int max);
void newEmployee();

//  KLASSER:
class Person {                   
protected:
    char* firstname;                //  Person's firstname.
    char  dob[DATELEN];   //  Date of birth format yymmdd

public:
    Person() {
        cout << "\nfirstname: ";
        cin.getline(firstname, MAXTXT); // This crashes the program after I've written in a firstname
        cout << "\ndob (yymmdd): "; cin.getline(dob, DATELEN); // This seems to work
    }
};

class Grownup : public Person {  
protected:
    char* lastname;              //  Grownups' lastname

public:
    Grownup() {
        cout << "Lastname: "; cin.getline(lastname, MAXTXT); // The program also crashes when entering lastname
    }
};



class Employee : public Grownup {        //  Employee class
private:
    int      nr;                       //  Unique employee ID number

public:
    Employee() {
        cout << "\n\nWARNING: This message should never be displayed\n\n";
    }

    Employee(int n) {
        nr = n; // Sets the nr to whatever is sent in the parameter
    }

};

//  GLOBAL VARIABLES
Employee* employees[MAXEMP + 1];     //  Array with pointers to all the employees
int lastUsed;                //  Last used empolyee "array number"

                               //  MAIN PROGRAM
int main() {
    char command;                //  Users wish/command

    printMenu();                  //  Prints menu with command options

    command = read();             //  Read users command wish
    while (command != 'Q') {
        switch (command) {
        case 'N': newEmployee();        break;   // Add a new employee
        default:  printMenu();      break;   // Print menu
        }
        command = read();           // Reads users command wish
    }
    return 0;
}

//  FUNCTION DEFINITIONS
void printMenu() {
    cout << "\n\nCOMMANDS AVAILABLE:";
    cout << "\n\tN - New employee";
    cout << "\n\tQ - Quit";
}


char read() {                     //  reads and returns in uppercase
    char ch;
    cout << "\n\nCommand:  ";
    cin >> ch;  cin.ignore();
    return (toupper(ch));
}
//  Reads leadtext (t), read and
//    return a number between min and max
int read(const char* t, int min, int max) {
    int number;
    do {
        cout << '\t' << t << " (" << min << '-' << max << "):  ";
        cin >> number;  cin.ignore();
    } while (number < min || number > max);
    return number;
}


void newEmployee() {                    //  N - NEW EMPLOYEE:
    if (lastUsed <= MAXEMP) {   // read employeenumber
        employees[++lastUsed] = new Employee(read("Employee nummer", 0, 9999));
    }
    else cout << "\nMax amount of employees reached";
}

Answer 1

firstname is an uninitialised pointer.

It does not point to anything.

You asked cin.getline to write to the buffer it points to.

Whoops!

---

Immediately underneath you "got it right" with dob ; why not make firstname an array as well?