Re: Accessing types in base class?

From:
"Abhishek Padmanabh" <abhishek.padmanabh@gmail.com>
Newsgroups:
comp.lang.c++
Date:
Sat, 27 Mar 2010 18:40:56 +0800
Message-ID:
<hoknch$ola$1@news.eternal-september.org>
"none" <""mort\"@(none)"> wrote in message
news:4badd7b4$0$281$14726298@news.sunsite.dk...

I have this base class:

template<typename J>
class Processor {
public:
  const unsigned int Dimension = J::Dimension;
  typedef typename J::ImageType ImageType;

  Processor ();
  virtual ~Processor ();

};
#endif

In a sub class I need to use the types from the base class:

  template <typename J>
  class SubProcessor : public Processor<J>{
  public:

    void test(ImageType image) {
       // do stuff

    }

};

But that is not possible! The base class type "ImageType" is not visible
in the sub class. In the sub class I could just do the same as in the base
class:

  typedef typename J::ImageType ImageType;

but what is the point of using inheritance then?


You would need to do something like this, although the initialization of the
const member in the base class is not valid, (and hence commented out):

template<typename J>
class Processor
{
 public:
   //const unsigned int Dimension = J::Dimension;
   typedef typename J::ImageType ImageType;
   Processor ();
   virtual ~Processor ();
};
template <typename J>
class SubProcessor : public Processor<J>
{
 public:
   void test(typename Processor<J>::ImageType image) {
      // do stuff
   }
};

 

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