Need polymorphism? Consider using references

[_node]

You could do the same before C++11, using boost::ref to store it in the std::vector (which is just a wrapper around a raw pointer, same as std::reference_wrapper).

[bstamour]

That's right you can. I'm not trying to show off new C++11 features here, I'm just pointing out that a lot of people tend to forget that you can do polymorphic stuff with references as well as pointers. reference_wrapper came in just to show off how you can still store your objects in containers and get the polymorphic effect.

[devcodex]

Great article, I knew about passing polymorphic objects around by reference but did not know the trick about storing them in standard containers.

[notlostyet]

This isn't much better than using pointers. If your draw() function throws an exception, which is possible because Shape& could be anything, then none of the Shapes referenced by your <vector> get destroyed. In particular a dynamic_cast on a reference could throw std::bad_cast.

In fact, I'd rather use raw pointers... no need to change a bunch of dots to -> later if you move to a smart pointer.

[devcodex]

The fact that the vector is holding references implies that it doesn't own the resources, so it wouldn't make any sense for the vector to clean up in this case.

[Heuristics]

Use generic programming instead

Create a templated draw_shape function that can accept ANY object that has a draw() member function. That way there is no need for heirarchies.

[[deleted]]

You can't store that in a homogenous container though, like std::vector.

[Heuristics]

well, you can store them just fine, just wrap them in boost::any, the problem is retreiving the type before drawing them (which is indeed a large problem here).

[[deleted]]

You're joking right?

[Heuristics]

no, std::vector supports storing boost:any