Question

Lets say I’ve got something like the following:

class A { virtual void g() = 0 }

class B : public A { virtual void g() { ... } }
class C : public A { virtual void g() { ... } }

... f(bool x)
{
  if (x) { return B(); } else { return C(); }
}

bool get_boolean();

int main()
{
  bool b = get_boolean();
  ... x = f(b);
  x.g();
}

Is there anyway to do something like the above without calls to new, i.e. solely on the stack?

Answer 1

In function f objects B() or C() are both temporary, so you can only return them from f by value.

Maybe boost::variant is for you. Then you don’t even need to have the method virtual or derive from a common base class.