Re: Implementation of abstract classes

James Kanze <>
Sat, 20 Sep 2008 12:15:41 -0700 (PDT)
On Sep 20, 6:07 pm, Rune Allnor <> wrote:

I have some classes which are derived from some base:

class base {
  void foo();
  void bar();

class a : public base {

class b: public base{

The problem is as follows:

1) I would like to prevent users from making instances of
   class base
2) There are no overloaded functions beween the base class
   and the derived classes, so I can not use the usual

   virtual void overloaded_function() = 0;

   in the base class.

As far as I can see, there are two ways to proceed:

1) make some virtual dummy function that the
   derived classes need to implement
2) Hide the constructor of base as protected.

From a semantic point of view the latter solution
seems the more elegant. Is this a good solution
or are there traps or snags associated with it?

I don't know about elegance, but the second solution is
certainly the usual solution.

James Kanze (GABI Software)
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