Question

I’m a Java/PHP programmer learning C++.

I’ve created a class called UserAccount and a class called Database.

I have an input file with five names:

Bob
Sam
Jane
Mark
Ann

I have the following (pseudo)code:

UserAccount *ua;
while (reading through the list of names, line by line) {
    ua = new UserAccount(name); // Create a new user based on this name
    Database->add(ua); // Add the user to the database
}

Database->listAllUsers();

The output should mirror the input file. Instead, I get:

Ann
Ann
Ann
Ann
Ann

I assume this has something to do with pointers, but I can’t figure it out. I think I’ve provided enough information to identify the problem, but if the (pseudo)code above looks correct, I can provide more.

Answer 1

To follow up from my comments. You are likely running afoul of pointers, the std::string class will give you behaviour much more similar to that of Java.

The simplest solution will be to use the string strdup() call.

#include <cstring> // provides C string interface

UserAccount::UserAccount(char *n) {
    name = strdup(n);
}

UserAccount::~UserAcount() {
    // This is older C style, cleanup. Need or the memory will "leak".
    free(name);
    // You could also use: delete[] name;
}

Alternatively you could use std::string, but I’ll leave that to your learning process. There is a lot of information on pointers out there, it will help your learning to understand pointers intimately.

// e.g.
char *str1 = "ann";
char *str2 = "bob";
str1 = str2;
// Both equal "bob".
str1 = "carol";
// Both equal "carol"!

Good luck.