vector<>::iterator question [SOLVED]

[captjack]

This is probably so simple that I can't see the obvious right in front of me. Nevertheless, I've thrown my hands in the air and pitch this to you guys:

Code: Select all

class MapObject {
public:
     int get_x();     // method implementation is obvious so i'll spare you the details
     int get_y();     // ditto
     ...
private:
     int x;
     int y;
     ...
};

Code: Select all

class Map {
public:
     void map_debug();
     ...
private:
     vector<MapObject*> mapObjects;
     ...
};

void Map::map_debug()
{
     ...
     for (vector<MapObject*>::iterator i = mapObjects.begin(); i != mapObjects.end(); i++)
          dbg.Print("(x, y) = (%d, %d)\n", i->get_x(), i->get_y());          // thanks gyrovorbis for debug singleton vid
}

Let's assume I didn't make a typo, and all necessary #include's are there, because the code compiles fine except for the vector<MapObject*>::iterator line.

Code: Select all

error C2839: invalid return type 'Object **' for overloaded 'operator ->'
error C2039: 'get_x' : is not a member of 'std::_Vector_iterator<_Ty,_Alloc>'

If I change Map::map_debug() to:

Code: Select all

void Map::map_debug()
{
     ...
     for (unsigned int i = 0; i < mapObjects.size(); i++)
          dbg.Print("(x, y) = (%d, %d)\n", mapObjects[i]->get_x(), mapObjects[i]->get_y());
}

then I get a successful compile and the intended output in the debug log, which is the (x, y) coordinates of map objects pushed into the vector container.

Why the hell can I not use the idiomatic vector<MapObject*>::iterator? I get the feeling that I'm not redirecting a pointer correctly, but I'm baked.

-capt jack

[captjack]

Oh, Jesus!

I took all that time to post my problem with such pretty formatting ---- and then I figured out the problem!

Code: Select all

...
void Map::map_debug()
{
     for (vector<MapObject*>::iterator i = mapObjects.begin(); i != mapObjects.end(); i++)
          dbg.Print("(x, y) = (%d, %d)\n", (*i)->get_x(), (*i)->get_y());
}

When one sleeps on a problem overnight, one should try to work on said problem the next day before one goes to the trouble of posting a tome.

-capt jack

[MarauderIIC]

When using non-standard types, ++i is a bit faster. I think the resources thing has a "how to use STL properly" link, and it includes stuff like that.

[captjack]

When using non-standard types, ++i is a bit faster. I think the resources thing has a "how to use STL properly" link, and it includes stuff like that.

Oh, crap. That was a cut n' paste boo-boo, but thanks for spotting it and bringing it up. Your point is one that does bear repeating now an again.

BTW, thanks for the OO design reply. I got the idea for MapObjects from your code which was more approachable than what I had originally wrote.

-capt jack

[avansc]

class Map : public vector<MapObject*>
{
}

if you wanna really OO it.

[captjack]

class Map : public vector<MapObject*>
{
}

if you wanna really OO it.

Nice! A little more step-wise refinement never hurt a source file. It pays to remember the expanse of inheritance. It also pays to not do this when you're tired.

Ever get so caught up in coding that you forget to use the fundamentals?

-capt jack

[MarauderIIC]

Neat, avansc.