Question

That may sound a little confusing. Basically, I have a function

CCard newCard() 
{
    /* Used to store the string variables intermittantly */
    std::stringstream ssPIN, ssBN;
    int picker1, picker2;
    int pin, bankNum;

    /* Choose 5 random variables, store them in stream */
    for( int loop = 0; loop < 5; ++loop )
    {
        picker1 = rand() % 8 + 1;
        picker2 = rand() % 8 + 1;
        ssPIN << picker1;
        ssBN  << picker2;
    }
    /* Convert them */
    ssPIN >> pin;
    ssBN  >> bankNum;

    CCard card( pin, bankNum );
    return card;
}

that creates a new CCard variable and returns it to the caller

CCard card = newCard();

My teacher advised me that doing this is a violation of OOP principles and has to be put in the class. He told me to use this method as a constructor. Which I did:

CCard::CCard()
{
    m_Sperre   = false;
    m_Guthaben = rand() % 1000;

    /* Work */

    /* Convert them */
    ssPIN >> m_Geheimzahl;
    ssBN  >> m_Nummer;
}   

All variables with m_ are member variables. However, the constructor works when I initialize the card normally

CCard card();

at the start of the program. However, I also have a function, that is supposed to create a new card and return it to the user, this function is now broken.

The original command: card = newCard(); isn’t available anymore, and card = new CCard(); doesn’t work. What other options do I have? I have a feeling using the constructor won’t work, and that I probably should just create a class method newCard, but I want to see if it is somehow at all possible to do it the way the teacher wanted.

This is creating a lot of headaches for me. I told the teacher that this is a stupid idea and not everything has to be classed in OOP. He has since told me that Java or C# don’t allow code outside of classes, which sounds a little incredible. Not sure that you can do this in C++, especially when templated functions exist, or generic algorithms. Is it true that this would be bad code for OOP in C++ if I didn’t force it into a class?

EDIT:

I would like to thank everyone for their helpful answers! However, I believe that my phrasing of the question is a little screwed up, and I think people don’t understand what I am looking for.

I do not want to initialize another member of type CCard. I want to intitialize

CCard card once and then give card new values through the constructor, because this is what the teacher told me to do. I do not want to create a new CCard object, just use the same variable with new values over again.

This is why I said it probably won’t work with the constructor. So I have a function that is supposed to take the initialized variable card and then call the constructor again( “What?” is what I told the teacher ) and then give it new values.

Example code:

void foo()
{
    /* Initialize card with constructor */
    CCard card;
    /* Give it new values through the constructor AGAIN... */
    card;
}

This is the actual question. I’m sorry if I confused everybody xD

Answer 1

Just some basic pointers, because you have some misunderstandings.

This doesn’t intialize a CCard, object. It declares card to be a function returning a CCard and taking no parameters.

CCard card();

If you want to construct a CCard object then just do this.

CCard card;

Your constructor will be called and card should be initialized correctly.

The expression new CCard() dynamically creates a CCard object and “returns” a pointer to a CCard object which you would then need to delete. I don’t recommend using this until you’ve successfully created and understood using local objects first.

EDIT in response to question edit

A constructor can only be called once in an object’s lifetime so you can’t ever ‘re-construct’ an object. If your class is assignable, though, you can typically assign it the value of a default constructed temporary:

card = CCard();