Always declare a polymorphic class' copy constructor as privatethis becomes important when you want to use a class in a container class for cloning.
The container class CHolder is a templatized class that holds generic objects. You also have a polymorphic class named CBase and its subclasses CDerived1 and CDerived2.
Suppose the client is storing objects of type CBase:
CHolder<CBase *> holder;
Consider another container instance:
CHolder<CBase*> holder1 = holder;
You need to copy the contained objects in CHolder
's copy constructor. However, this results in slicing if the default copy of the contained object's ctor
is involvedbecause the copy in C++ is always static. Thus, you should declare the virtual clone method in CBase
and override in derived.