On Oct 18, 4:40 am, Adam Nielsen <adam.niel...@remove.this.uq.edu.au>
wrote:
> Hi everyone,
>
> Yet another syntax problem that's baffling me with templates. I want to
> instantiate a template with a single parameter as per normal, however
> the parameter is actually a template class itself, with all *its*
> parameters filled out (in the form of a typedef.) I can't work out how
> to break apart the typedef to reveal what data types were used to create
> it in the first place.
>
> Here is some example code that demonstrates the problem. I've tried
> every syntax I can think of but I haven't managed to hit upon the right
> one yet! Any suggestions would be much appreciated.
>
> Many thanks as always,
> Adam.
>
> #include <iostream>
>
> template <class TFrom, class TTo>
> class CLinkData;
>
> class A { };
> class B { };
>
> typedef CLinkData<A, B> MyLink;
>
> // How do you declare the template to accept a CLinkData parameter, but
> // broken out into its component types?
> //template <template <class TLinkFrom, class TLinkTo> class TLinkData>
> //template <template <class TLinkFrom, class TLinkTo>
> // class TLinkData<TLinkFrom, TLinkTo> >
> template <class CLinkData<TLinkFrom, TLinkTo> >
> void createStoredLink(void)
> {
> std::cerr << "CLinkData types are " << typeid(TLinkFrom).name() <<
> " and " << typeid(TLinkTo).name() << std::endl;
> // TLinkFrom should be A, and TLinkTo should be B, the types used
> // to declare MyLink.
> return;
>
> }
>
> int main(void)
> {
> createStoredLink<MyLink>();
> return 0;
>
>
>
> }- Hide quoted text -
>
> - Show quoted text -

Hi,
try one of the following.
Bye,
Francesco B.

#include <iostream>
#include <typeinfo>

template< typename T >
struct CTypeFromType
{};

template <class TFrom, class TTo>
class CLinkData;


class A { };
class B { };


typedef CLinkData<A, B> MyLink;

// first method

template< typename TFrom, typename TTo >
void createStoredLinkAux( CTypeFromType< CLinkData< TFrom, TTo > > )
{
std::cerr << "CLinkData types are " << typeid(TFrom).name() <<
" and " << typeid(TTo).name() << std::endl;

return;



}

template < typename T >
inline void createStoredLink(void)
{
createStoredLinkAux( CTypeFromType< T >() );
}

// second method

template< typename T >
struct CCreateStoredLink
{};

template< typename TFrom, typename TTo >
struct CCreateStoredLink< CLinkData< TFrom, TTo > >
{
static void Do()
{
std::cerr << "CLinkData types are " << typeid(TFrom).name() <<
" and " << typeid(TTo).name() << std::endl;

return;
}
};

int main(void)
{
createStoredLink<MyLink>();
CCreateStoredLink<MyLink>:o();
//createStoredLink< int >(); //compile time error
//CCreateStoredLink< int>:o(); // compile tiem error
std::cin.get();
return 0;
}