Why can't my silly cardgame classes talk to each other? [closed] - c++

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I have tried to make some sort of card game here but the classes for the holder / cardpile don't give away right things to the reciver/player and I don't know how to sort this out.
Here is the program:
#include <iostream>
using namespace std;
class subclass // like a card
{
public:
subclass();
subclass(int x);
int nummer;
int getnummer();
};
subclass::subclass():nummer(0){}
subclass::subclass(int x):nummer(x){}
int subclass::getnummer()
{
return nummer;
}
holder class:
class holder // like a cardpile
{
public:
holder();
subclass cardpile[2];
subclass* pile; // a cardpile which has 2 cards, with nummber 1 and 2.
subclass* getsubclass(int i); // take first or second card.
};
holder::holder()
{
subclass first(1*3);
subclass second(2*3);
pile=cardpile;
pile=&first;
pile++;
pile=&second;
pile--;
}
subclass* holder::getsubclass(int i) //1 eller 2.
{
return pile+i;
}
reciver class/ the player
class reciver // like a player
{
public:
subclass part_of_holder;
reciver();
void getsubclass( subclass* in); // give this card to player from this pointer
void showinside(); // what card do player have
};
reciver::reciver():part_of_holder(){}
void reciver::getsubclass( subclass* in)
{
part_of_holder=*in;
}
void reciver::showinside() // what card do player have
{
cout<< part_of_holder.getnummer();
}
and the main
int main()
{
holder cardpile;
reciver player;
cout << "first card should be 1*3 and it is : " ;
player.getsubclass(cardpile.getsubclass(0));
player.showinside();
cout << endl <<"first card should be 2*3 and it is : " ;
player.getsubclass(cardpile.getsubclass(1));
player.showinside();
return 0;
}
In the end all I get is nonsence

Answer 1

holder::holder()
{
subclass first(1*3);
subclass second(2*3);
pile=cardpile;
pile=&first; // WRONG
pile++;
pile=&second; // WRONG
pile--;
}
The two lines above dont do what I suspect you think they do.
If you are trying to assign in the cardpile you would need something more like this:
cardpile[0] = first or *pile = first.
Sadly they wont work, since you dont have copy constructors. You also dont have any way to set a subclass's nummer field once constructed, so you are slightly doomed.
Add a setter function to the get instruction, and you could write this:
cardpile[0].setnummer(first.getnummer());

Answer 2

This is not going to work
holder::holder()
{
subclass first(1*3); // create temporary
subclass second(2*3); // create another temoporary
pile=cardpile; // assign member pointer to another member!!!
pile=&first; // assign member pointer to temporary
pile++;
pile=&second; // assign member pointer to temporary
pile--;
}
// member pointer pile points to object that no longer exists!!!
Basically once you create an instance of holder its internal pile pointer points to an object that no longer exists and that alone makes your class unstable because your getsubclass method returns an offset of this pointer - thus any attempt to dereference it will likely segfault.
In all honesty you would be better to start off again from scratch but a way of ensuring that you assign these temporaries to your member array would be
cardpile[0] = subclass(1*3);
cardpile[1] = subclass(2*3);
pile = cardpile;
however, the way this code is written is not a good design and I would advise starting from scratch when your grasp of C++ is better.