Re: How to detect overwritten virtual method in base class?

macracan wrote:
....


How about this:

// override check helper class
struct OverriddenCheck
{
     friend class WindowSink;
     friend void Subscribe(WindowSink &sink);

     bool m_checking;

     OverriddenCheck() : m_checking() {}

     private:
     enum OverrideState { Overridden, Default };

     public:
     void IsOverridden()
     {
        if ( m_checking ) throw Overridden;
     }

     private:
     void IsDefault()
     {
        if ( m_checking ) throw Default;
     }

}

struct WindowSink
{
   OverriddenCheck m_check;

// ...
   // default empty handlers
   virtual void Move(int x, int y)
   {
       IsDefault();
   }
   virtual void Draw()
   {
       IsDefault();
   }

private:
   void IsDefault() // can only be called by methods in WindowSink
   {
      m_check.IsDefault();
   }
};
//...
struct MyWindowSink : public WindowSink
{
   // overwrite Draw only
   void Draw()
   {
      m_check.IsOverridden();
   }
};

void Subscribe(WindowSink &sink)
{
   static WindowSink sinkref; // some reference to compare with
   long mask = 0;

   sink.m_check.m_checking = true;

   try {
       sink.Move(0,0);
       // improperly implemented sink
       abort();
   } catch ( OverriddenCheck::OverrideState l_override )
      if ( l_override == Overridden ) mask |= 1;
   }

   try {
       sink.Draw();
       // improperly implemented sink
       abort();
   } catch ( OverriddenCheck::OverrideState l_override )
      if ( l_override == Overridden ) mask |= 2;
   }

   // there is probably some kind of template you can use to
   // eliminate most of the try-catch blocks and write somthing like:

   CheckOverride( sink, &WindowSink::Draw, mask, 1 );
   CheckOverride( sink, &WindowSink::Move, mask, 2 );

   sink.m_check.m_checking = false;

   // subscribe to messages based on mask
   XSelectInput(/* some other params */, mask);
}
int main()
{
   MyWindodwSink sink;
//...
   Enable(sink);
// ...
   return 0;
}