using map, list etc. in const methods

From: Christof Krueger (donotspamnews_at_pop2wap.net)
Date: 01/23/04 

Date: Fri, 23 Jan 2004 20:12:11 +0100

Hello,

I'm quite new to C++ so maybe there's something I miss.
I write a simple board game. It has a board class. This class has a
method that returns the count of pieces a player has on the board. Since
this function does not change anything in the class I declared it as
const. To count all pieces of a given color the functions iterates
through a "map" of CNode-pointers. "CNode" is another class that is
irrelevant to the problem.

Here comes the function: (EColor is an enum of colors, not important here)

int
CBoard::countPieces(EColor color) const
{
   // "nodes" is a private class member
   // with type map<string,CNode*>
   int count = 0;
   for (map<string,CNode*>::iterator i=nodes.begin();
        i != nodes.end();
        i++)
   {
     // do something with (*i)
     // ...
   }
   return count;
}

The compiler refuses to compile the code, because I violate the
constness of the function in the line where I declare the iterator.
Is there a proper way (or workaround) to leave the function const?

Another point: I've heard, that it is not good to store pointers to
objects in stl-containers like map, list, vector etc. because of
ownership problems (?). Do you know a good webpage or tutorial about
this topic? I would like to learn how to do it the right way.
There are a lot of classes in the STL and I would like to know how to
use their whole power. At the moment I'm just using lists, vectors and
maps in lack of a good book or online tutorial discussing the STL in detail.

Thanks in advance! 

-- 
Regards,
   Christof Krueger
Remove "donotspam" if you want to email me.

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