[Greenengine-developer] a note on dynamic casts of shared_ptr

[Jeremy B. <bel...@gm...>]

Given the following classes:

class base {
    public:
       virtual ~base() {}
};

class sub : public base {
    public:
       virtual ~sub() {}
};

The following does NOT work:
int main()
{
    shared_ptr<base> b(new base()); // BAD
    shared_ptr<sub> a(dynamic_pointer_cast<sub>(b));
    assert(a.get()); // ASSERT WILL FAIL
    return 0;
}

The following WILL work:
int main()
{
    shared_ptr<base> b(new sub()); // GOOD
    shared_ptr<sub> a(dynamic_pointer_cast<sub>(b));
    assert(a.get()); // ASSERT WILL PASS
    return 0;
}

It basically means I have to essentially rewrite any subclass functions 
that instantiate objects, like TemplateTable::Instantiate all need to be 
rewritten in the subclasses to make a new instance of the subclass they 
work with, rather than the base class. There may be other places where I 
should do this, I'll have to see.

Regards,
Jeremy