Re: mandatory/optionally overridable virtual functions
Dilip wrote:
In a polymorphic hierarchy is it common practice to have public
virtual functions in the base class with a default empty
implementation and let the derived classes decide whether they want to
override it or not?
It's one of three common practices. The other two are to leave the
function pure and to actually implement proper behaviour for the base
class object. Come to think of it, that's pretty much all the choices
one has WRT virtual functions in the base class. You can also have
an implementation of a pure function, but I'd guess that it's less
common (except for destructors, maybe).
In such cases what would be the access levels of
those functions in both base and derived classes?
There is no common rule about it. Do as your model domain requires.
struct AbstractBase
{
virtual void mandatory_func() = 0;
virtual void optional_func() { }
};
struct concretebase1 : public AbstractBase
{
virtual void mandatory_func() { }
};
struct concretebase2 : public AbstractBase
{
virtual void mandatory_func() { }
virtual void optional_func() { // do something cool }
};
on the face of it, it does seem natural but somehow I can't get it out
of my mind that I just keep adding virtual functions to AbstractBase
for every *specific* action I want to perform from one of the derived
classes.
Well, *that* doesn't seem sensible. Your motivation here is either
wrong or unclear.
If I have a lot of such operations I am concerned there
would be a virutal function bloat in AbstractBase.
What's a virtual function bloat? Why are you concerned with it?
Are my fears misplaced?
Fears of what? The bloat? Misplaced.
V
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