Re: How to enforce a virtual fn is overloaded by derived class?
Chris Morley wrote:
I need to enforce requirement that the programmer overloads a particular
virtual function in all derived classes.
You mean override, not overload. Overloading means providing functions with
the same name but different parameters.
class base {
public:
virtual void foo() {} // base has some handler
};
class deriv1 : public base {
void foo() {} // good overridden
};
class deriv2 : public base {
}; // bad, no overload so I want compiler to choke
You can use a "pure virtual" function for that. Note that you can also
implement a pure virtual function.
The only drawback is that it doesn't force _every_ derived class to add an
override. If you derive from a class that implements it, you don't get any
notification. If you derive from the base but don't implement it, you also
only get an error if you try to instantiate an object of that class, just
like for class base.
I am using VS2008 (VC9) (not /clr) so it adheres to _some_ of the standard
;)
What I can do is...
class base_base abstract {
public:
... all fns ...
virtual void foo()=0;
};
If you now drop the "abstract", which is non-standard, you get a baseclass
that has a single, pure virtual function. What puzzles me here is that you
seem to know pure virtual functions, so either you misunderstand them a bit
or you want something different, which I in turn misunderstand. ;)
Uli
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