Parent* parameter, not using child function (virtual in parent)

Algar · #1 04-Nov-2007, 00:17

I am not sure if I am creating a parent class or a child class with this code, but either way, the parent function which is virtual is being called rather then the child function that I want:

Heres various relevant code snippets:

CPP / C++ / C Code:

//The MapCell is a container class which has (among other things) a pointer to a TerBase (parent) with the following function:
//....
void MapCell::setTerrain(TerBase* newTerrain) 
{
	delete terrain;
	terrain = newTerrain;
	terrain->SetRect(left,top,right,bottom);
}
//...

//TerBase paint() declaration:
virtual void paint(CPaintDC* dc);

//Then I have a child of terbase...
class TerFlag : public TerBase 
//...
void paint(CPaintDC* dc);
//...

//Then I have my data manager class which has a 2d vector of MapCells with the following function:
void MapCtrl::setTerAt(const CPoint& index, const TerBase & terrain) 
{
	map[index.x][index.y].setTerrain(new TerBase(terrain));
	paintMap();
}

Hopefully thats just about covers everything. Heres my issue
When from my window event I call the function like this...

CPP / C++ / C Code:

pMap->setTerAt(pMap->pointToIndex(point), TerFlag());

I end up with either a TerFlag object using the TerBase paint() function or a TerFlag object. Either way what I want is a TerFlag object with the TerFlag paint() function !

Can anyone explain to me please what I should change ? I am assuming that its the "new TerBase(terrain)" line thats causeing the problems, but if I don't know in advance which child class is being passed, how can I get around this ?

Algar · #2 04-Nov-2007, 01:11

Yet another question I solved soon after posting...

I changed the intermedite function to receive a TerBase* instead of a TerBase object.

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Parent* parameter, not using child function (virtual in parent)

Re: Parent* parameter, not using child function (virtual in parent)