Probably a simple question

I am new and have been working my way through the tutorials and am now officially annoyed. I have started experimenting with classes and seeing how I can work them into a linked list style of operation. My code is here:

Code:

---


class Database
{
 public:
  // public variables
  char employee_name [50];  // employee name
  int id_number;              // identification number
  int group_number;            // group number
 
  Database ();                // constructor definition
  ~Database ();                // destructor definition
     
  Database *next;              // pointer to the next entry

 // function to add a new employee
  void add_new_user();

 protected:
  char supervisor [50];        // name of supervisor
  int ranking;                // ranking within group
  float salary;                // employee's salary
 
  void getsupervisor (char *super, int group);
  // determine the employee rank
  int getrank (int id, int group);   
  // determine the salary
  float getsalary (int rank, int group);
 
};

void Database::add_new_user( )
{
      char name [50];
      int group;
      int id;
      cout << "Enter the employee's name ";
      cin.getline (name, 50, '\n');
      cout << "Enter the employee's group ";
      cin >> group;
      cin.ignore();                // ignore enter
      cout << "Enter the employee's ID number ";
      cin >> id;
      cin.ignore();
     
      strncpy(employee_name, name, 50);
      group_number = group;
      id_number = id;
      ranking = getrank(id, group);
      salary = getsalary(ranking, group);
      getsupervisor(supervisor, group);

}   

int main ()
{
    Database *root;    // delcare a pointer to a root database
    Database *employee;  // declare a pointer to the employee database
    employee = root;                    // set the employee                           
   
    char entry;                        // entry selection

    while (entry != 'e')
    {
      cout << "(a)dd new employee \n";
      cout << "(p)rint all employees \n";
      cout << "(e)xit \n";
      cin >> entry;
     
      // switch statement for entry
      switch (entry)
      {
        case 'a' :
          employee -> next = new Database; // create a new database
          employee = employee -> next;    // set pointer to new employee
          employee.add_new_user();
          break;
        case 'p' :
          employee = root;
          while (employee != NULL)
          {
            cout << "Name: " << employee -> employee_name << "\n";
            cout << "Group: " << employee -> group_number << "\n";
            cout << "ID number " << employee -> id_number << "\n";
 
            employee = employee -> next;
          }
          cout << "Name: " << employee -> employee_name << endl;
          cout << "Group: " << employee -> group_number << endl;
          cout << "ID number " << employee -> id_number << endl;
          break;
        case 'e' :
          cout << "Ending" << endl;
          break;
      }
    } 
         
    cin.get();
}

---

When I get to employee.add_new_user, I get this error:

"141 C:\Documents and Settings\Owner\My Documents\dbase_exp.cpp `add_new_user' has not been declared" and I can't understand why. Could somebody enlighten me?

Thanks

Chris

Code:

---

#include <iostream>

using namespace std;

...

employee->add_new_user();

---

Code:

---

    Database *root;    // delcare a pointer to a root database
    Database *employee;  // declare a pointer to the employee database
    employee = root;

---

This is quite analogous to simpler code:

Code:

---

    int a, b;
    a = b;

---

a and b would be equal but still containing a garbage value. This is the same that happens in your code, you have invalid pointers that don't point to anything meaningful.

A very serious design problem is that you are reinventing a linked list, and exposing the mechanism of it to the users of the class (for example, the next pointer which is the "easiest-to-mess-up" thing in this code and should be encapsulated most carefully, is made public!). You are leaving the hardest stuff - managing the linked list - up to the user of Database.

If you are just learning classes, may-be you ought to start with something easier (e.g forget about your own linked list, and use std::list) and concentrate on good practices of class design (e.g data hiding) instead.