class Shape
{
public:
int width, height;
virtual int area() { return 0; }
};
class Square : public Shape
{
public:
int area() { return width*height; }
};
for(std::vector<Shape*>::iterator it = shapes.begin(); it != shapes.end(); it++)
{
Shape &s = **it;
s.area();
}
for(std::vector<Shape*>::iterator it = shapes.begin(); it != shapes.end(); it++){ Shape *s = *it; s->area();}
int main(){ std::vector<Shape*> v; Shape* s = new Square; v.push_back(s); Shape& s2 = **v.begin(); s2.area();}Quote:Original post by MrPickleEach overload is a distinct and different function, and each of them needs to exist as a virtual in the base class, yes.
do I have declare a virtual function for each overload?
Quote:Original post by taz0010No! This is completely false. Calling a virtual function from a reference or a pointer will do the same thing.
Functions are only called virtually when you use a pointer, so the line below can only call Shape members.
Shape s = **it;//make a copy into a new shape objects.area();//object has been sliced, this will always call Shape::areaQuote:No! This is completely false. Calling a virtual function from a reference or a pointer will do the same thing.
Quote:The only time slicing will occur is if you copy the object by value
B* der = new D(1,2,3);B* der2 = new D(4,5,6);B& ref = *der;B& ref2 = *der2;ref = ref2;Quote:Original post by taz0010Yeah, the references are like a "short-hand" for writing whatever they're bound do, so your example of "ref = ref2;" is the same as writing:B* der = new D(1,2,3);B* der2 = new D(4,5,6);B& ref = *der;B& ref2 = *der2;ref = ref2;
Quote:Original post by taz0010Quote:No! This is completely false. Calling a virtual function from a reference or a pointer will do the same thing.
Interesting. Didn't realise this.Quote:The only time slicing will occur is if you copy the object by value
I'm also getting slicing when I copy using references. (Which is in effect a copy by value of course)B* der = new D(1,2,3);B* der2 = new D(4,5,6);B& ref = *der;B& ref2 = *der2;ref = ref2;
This seems a little confusing. I think I'll stick to using pointers when inheritance is concerned.
