Re: deriving a class - extending enum

werasm wrote:


Forget it. _DO_ use enums. The hierarchy of exception classes is a good
idea, but _not_ as a replacement for enum constants as exception codes.
An attempt to introduce a separate exception class for every concrete
exception type will only lead to a disaster. In the exception hierarchy
the classes themselves are supposed to serve for a rough division of
various exception types into relatively large groups or..., well...
"classes" of exceptions. The concrete exception type within the class is
still best described with a enum constant.

Your original idea of "extending" the enum in the derived class can be
easily implemented as follows

 class BaseException {
 public:
   enum Type {
     firstEnum,
     secondEnum,
     next_enum_,
   };

   int m_something;
   ...
 };

 class DerivedException : public BaseException {
   typedef BaseException BASE;
 public:
   enum Type {
     oneMoreEnum = BASE::next_enum_,
     yetMoreEnum,
     stillMoreEnum,
     next_enum_
   };
   ...
 };

 class DerivedDerivedException : public DerivedException {
   typedef DerivedException BASE;
 public:
   enum Type {
     oneAdditionalEnum = BASE::next_enum_,
     anotherAdditionalEnum,
     moreAdditionalEnum,
     next_enum_
   };
   ...
 };

  // And so on...