Thread: Problem with a vector pointer

To put it brief:

Code:

class thisclass
{
  public:
    vector <someclass> *sc;
    thisclass(vector <someclass> &_sc)
    {
        sc = &_sc;
    }
    void somefunc(const int n)
    {
        int x, int y;
        if((x == someclass[n]->x) && (y == someclass[n]->y))
             dosomething();
    }
};

Get what I'm trying to do here and why it doesn't work (that's the part I do not know)?

Ah, that's just something I forget to do in the example, but consider as a real comparement in this situation. It should read something like:

int x = 13, y = 2;

But what I'm after is how to compare that 'x' element in the someclass-vector.

Code:

class Bomb
{
  public:
	Bomb(Player &_host, Map &_map, vector <Bomb> &_bombs)
	{
		...
		bombs = &_bombs;
	}
	...
	vector <Bomb> *bombs;
	void do_flames(const short coord, const short t, const bool xy)
	{
		short _x = x, _y = y;
		bool stop;
		tile mapt;

		for(int dir = 0;  dir < 2;  dir++)
			for(int i = coord;;)
			{
				...
				else if(isbomb(mapt))
					for(size_t n = 0;  n < bombs->size();  n++)
						if((_x == bombs[n]->x) && (_y == bombs[n]->y))
						{
							bombs[n]->timer = 0;
							break;
						}
			}
	}
	...
};

Results to:

[code]
G:\source\bombo>gxx main.cpp -lalleg -Wall
main.cpp: In member function `void Bomb::do_flames(short int, short int,
bool)':
main.cpp:254 (bombs[n]->x): base operand of `->' has non-pointer type `std::vector<Bomb,
std::allocator<Bomb> >'
main.cpp:254 (bombs[n]->y): base operand of `->' has non-pointer type `std::vector<Bomb,
std::allocator<Bomb> >'
main.cpp:256 (bombs[n]->timer): base operand of `->' has non-pointer type `std::vector<Bomb,
std::allocator<Bomb> >'
[/code}

vector <someclass> *sc; //??????????????

Code:

this is a vector of type someclass called sc

vector <someclass> sc; 

this is a vector of pointer to type someclass called sc

vector <someclass *> sc;

This is an iterator to be used with a vector of type someclass

vector <someclass>::iterator itr;

This is how you read through the vector using the iterator:

for(itr = sc.begin(); itr != sc.end(); ++)
{
    //x, y, and timer are public member variables in class someclass
    cout << itr->x << ' ' << itr->y << ' ' << itr->timer << endl;
}

this is how you read through the vector using [] operator
int index;

for(index = 0; index < sc.size(); ++index)
{
   cout << sc[index].x << ' ' << sc[index].y << ' ' << sc[index].timer << endl;
}

this is how you would use [] if sc holds pointers to someclass objects

for(index = 0; index < sc.size(); ++index)
{
  cout << sc[index]->x << ' ' << sc[index]->y << ' ' << sc[index]->timer << endl;
}

if you want to use an iterator to a vector of pointers to someclass it would look something like this:

vector <someclass *>::iterator pItr;
for(pItr = sc.begin(); pItr != sc.end(); ++pItr)
{
  cout << (*pItr)->x << ' ' << (*pItr)->y << ' ' << (*pItr)->timer << endl;
}

Assuming I haven't screwed up along the way.

So now I need to do a loop to the constructor like this (sorry, I don't have the time to test it first):

Code:

Bomb(vector <Bomb> &_bombs)
{
    for(size_t i = 0;  i < _bombs.size();  i++)  // I like this rather than those iterators...
        boms[i] = &_bombs[i];
}
vector <Bomb *> bombs;

But what does my first try, vector <Bomb> *bombs, do? Does it take 4 or bombs.size()*4 bytes of memory? Where does it point if I set it to &_bombs?


Thanks for your help