CODEWITHSUNDEEP
c++
Ryan
Ryan

Reputation: 61

Shuffle function does not work using a pointer

I recently started c++ and I created a class called Deck that pretty much creates a deck of cards. One of it's functionality is to shuffle a deck. I created a object of type Deck in main() and was able to called the shuffle() member function...which worked! However when I accessed the shuffle() function using a pointer, Xcode highlights:

Card u1 = *(cards[index]);

and outputs: 

Thread 1:EXC_BAD_ACCESS (code = EXE_1386_GPFLT)

Can anyone help me out here?

void Deck::shuffle()
{
    srand(static_cast<unsigned int>(time(0)));

    for(size_t x = 0;x<cards.capacity();x++)
    {
        int index = rand()%51;
        int index2 = rand()%51;

        Card u1= *(cards[index]);
        *cards[index] = *cards[index2];
        *cards[index2] = u1;
    }
}

int main()
{
    //Deck p;
    //p.shuffle(); //works!
    //p.Display();//works!
    Deck *p;
    p->shuffle(); //does not work!
}

Upvotes: 2

Views: 141

Answers (1)

Armen Tsirunyan
Armen Tsirunyan

Reputation: 133044

There are several errors in your code.

Pointer which points nowhere

Deck *p;
p->shuffle(); //does not work!

You've just created a pointer to a deck. Where is the actual deck to which the pointer points to?

You should do

Deck* p = new Deck;
p->Shuffle();

or

Deck theDeck;
Deck* p = &theDeck;
p->Shuffle();

Iterate till size, not capacity

for(size_t x = 0;x<cards.capacity();x++)

You are not allowed to access all elements within the vector's capacity. You should use x < cards.size()

Cards are not pointers, are they

Does your cards container hold pointers to cards? If it contains actual cards, not pointers to them, then your swap routine should not use dereferenceing (*cards[index] --> cards[index])

52 cards, not 51

Incidentally, if cards had 52 elements, then you should rand()%52, not 51.

Upvotes: 2

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