Initializing an array of objects

Question

I'm currently working on a card game, and I'm having trouble with some initialization code:

// in my class...
Card cards[20];
// in method...
for(int i = 0; i <= 20;i++)
    cards++ = new Card(i, /*i as char +*/ "_Card.bmp");

The trouble is that my compiler's telling me that cards++ is not an l-value. I've read up on the whole pointer-array equivalence thing, and I thought I understood it, but alas, I can't get it to work. My understanding is that since cards degrades to a pointer, and the new operator gives me a pointer to the location of my new instance of Card, then the above code should compile. Right?

I've tried using a subscript as well, but isn't cards+i, cards++, and cards[i] just 3 ways of saying the same thing? I thought that each of those were l-values and are treated as pointers.

Answer 1

Card cards[20];

cards is already an array of objects. They are constructed with the default constructor(constructor with no arguments). There is no need to new again. Probably you need a member function equivalent to constructor arguments and assign through it.

for ( int i=0; i<20; ++i ) // array index shouldn't include 20
   cards[i].memberFunction(/*....*/);

Even simpler is to use std::vector

std::vector<Card> cards;
for( int i=0; i<20; ++i )
    cards.push_back(Card(i, /*i as char +*/ "_Card.bmp"); )

Answer 2

The code Card cards[20]; already creates an array of 20 Card objects and creates them with the default constructor. This may not be what you want given your code.

I would suggest using vector instead.

std::vector<Card> cards;

for(int i = 0; i < 20;i++)
{
    cards.push_back(Card(i, /*i as char +*/ "_Card.bmp"));
}

Note that your for loop goes from 0 to 20 and thus one past the end of the array.