Dereferencing a boost::ptr_vector

Question

So right now I have the following:

        boost::ptr_vector <Customer> cvect;

         ifstream cDbase("datafiles/customers.txt");

        while (cDbase.good())
        {
            while (!cDbase.eof())
            {
                cDbase >> newCust;

                Customer* c = &newCust;
                cvect.push_back(c);

            }
        }


        for (unsigned int loop = 0; loop < cvect.size(); loop++)
            {   
                cout << cvect[loop];
            }

When I try to print the customer details, it prints out blank lines. How do I dereference ptr_vector properly?

Answer 1

The Boost pointer-containers are for containers which own dynamically-allocated objects. So to use it as intended, you'd do this:

while (cDbase >> newCust) {
  cvect.push_back(new Customer(newCust));
}

(Note: never loop on eof() ).

However, do you really need to store them dynamically? How about simply this:

std::vector<Customer> cvect;

ifstream cDbase("datafiles/customers.txt");

while (cDbase >> newCust) {
  cvect.push_back(newCust);
}

Answer 2

If newCust is a local variable, you push a pointer to a local variable into the vector which will not work.

Instead you have to create a new object each time through the loop. A simple solution would look something like this:

while (cDbase >> newCust)
    cvect.push_back(new Customer(newCust));

This might require you to have a proper copy-constructor in place.