Re: error c2259 - (TEMPLATE CLASSES AND INHERITANCE)
[ news_user ] <waste-paste@hotmail.com> wrote:
class Processor_Base
{
public:
virtual double getTimingMS(void) = 0;
};
template<class Feature_Detector_>
class Processor_Feature_Detector : public Processor::Processor_Base
{
// ...
};
After i created an Template object:
//PROCESSORS
Processor::Processor_Feature_Detector<Processor::Alg::Feature_Detector_OpenCV>
m_processor_feature_detector;
I want to push it to the STL vector. That's where i get the error:
Processor::Processor_Base m_processor_feature_detector_base =
static_cast<Processor::Processor_Base>( m_processor_feature_detector
); //ERROR C2259
m_pipeline->add_processor( &m_processor_feature_detector_base );
You are trying to create an object of type Processor_Base and
copy-initialize it from m_processor_feature_detector. Of course
Processor_Base cannot be instantiated. What you want is
m_pipeline->add_processor( &m_processor_feature_detector );
or, if you insist on an intermediate variable:
Processor::Processor_Base* m_processor_feature_detector_base =
&m_processor_feature_detector;
m_pipeline->add_processor(m_processor_feature_detector_base );
or
Processor::Processor_Base& m_processor_feature_detector_base =
m_processor_feature_detector;
m_pipeline->add_processor(&m_processor_feature_detector_base );
Pay attention to stars and ampersands here.
"It is not possible to create an object from the base class"
That's not the error message says. It says "cannot instantiate abstract
class" - as in, class that has any pure virtual methods, which
Processor_Base definitely does.
Is it possible to derive a Template class from an interface?
Yes. What is not possible is to create an instance of an interface.
Template classes do not have a constructor/destructor.
Do too.
How is
inheritance working with them?
The same way it's working with any other class. I'm not sure I
understand this question.
--
With best wishes,
Igor Tandetnik
With sufficient thrust, pigs fly just fine. However, this is not
necessarily a good idea. It is hard to be sure where they are going to
land, and it could be dangerous sitting under them as they fly
overhead. -- RFC 1925