Re: templated class : constructor specialization

From:
JSeb <JSebBolduc@gmail.com>
Newsgroups:
comp.lang.c++.moderated
Date:
Tue, 8 Apr 2008 08:06:36 CST
Message-ID:
<f66a9d1c-49aa-4613-98ed-bd488039796b@u69g2000hse.googlegroups.com>
Okay: here's what I came up with, after your much appreciated
comments. Instead of a helper class, I'm trying to use a common base
class for the main template, and its specialization.

Any comment will be much appreciated!

Thanks again.

==========================

// *** COMMON BASE CLASS ***
template <typename T>
class ATemplateClassCommonInterface
{
protected:
   const T* const mpData;
   int mCounter;
protected:
   ATemplateClassCommonInterface(const T* apData, int aCounter = 0) :
mpData(apData), mCounter(aCounter) { }
public:
   virtual ~ATemplateClassCommonInterface() { }
   // COMMON INTERFACE --- TO BE IMPLEMENTED IN DERIVED TEMPLATES
   virtual void specializedMethod() = 0;
   // COMMON INTERFACE --- IMPLEMENTED HERE
   void commonMethod()
   {
      std::cout << "commonMethod : mCounter = " << this->mCounter <<
std::endl;
      this->mCounter++;
   }
};

// *** MAIN CLASS TEMPLATE ***
template <typename T>
class CTemplateClass : public ATemplateClassCommonInterface<T>
{
public:
   CTemplateClass(const T& aData) :
ATemplateClassCommonInterface<T>(new T(aData), 0)
   {
      std::cout << "CTemplateClass<T>::CTemplateClass : *mpData = "
<<
            *(this->mpData) << std::endl;
   }
   virtual ~CTemplateClass()
   {
      delete this->mpData;
   }
   void specializedMethod()
   {
      std::cout << "CTemplateClass<T>::specializedMethod" <<
std::endl;
   }
};

// *** SPECIALIZED CLASS TEMPLATE ***
template <typename T>
class CTemplateClass<T*> : public ATemplateClassCommonInterface<T>
{
public:
   CTemplateClass(const T* apData) :
ATemplateClassCommonInterface<T>(apData, 10)
   {
      std::cout << "CTemplateClass<T*>::CTemplateClass : *mpData = "
<<
            *(this->mpData) << std::endl;
   }
   virtual ~CTemplateClass()
   {
      // Show some manners.
      //delete this->mpData;
   }
   void specializedMethod()
   {
      //AHelper_TemplateClass<T>::specializedMethod(this);
      std::cout << "CTemplateClass<T*>::specializedMethod" <<
std::endl;
   }
};

==========================

In the Main function,
   CTemplateClass<int>* pTC1 = new CTemplateClass<int>(10);
   CTemplateClass<int*>* pTC2 = new CTemplateClass<int*>(new int(15));
   pTC1->commonMethod();
   pTC2->commonMethod();
   pTC1->specializedMethod();
   pTC2->specializedMethod();
   delete pTC1;
   delete pTC2;

Output:
   CTemplateClass<T>::CTemplateClass : *mpData = 10
   CTemplateClass<T*>::CTemplateClass : *mpData = 15
   commonMethod : mCounter = 0
   commonMethod : mCounter = 10
   CTemplateClass<T>::specializedMethod
   CTemplateClass<T*>::specializedMethod

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