No match found for template template function

Question

The following code fails to compile under g++, with the following error:

"no matching function for call to 'GetRecById(int&, NULL)'":

template < typename T >
struct DummyLookup
{ 
    static bool DoLookup( T& rec, const char* id )
    {
        rec = 123;
        return true;
    }
};

template < typename T,
           template <class> class LookupPolicy
         >  
static bool GetRecById( T& rec, const char* id )
{        
    return LookupPolicy<T>::DoLookup( rec, id );
} 

static void testLookup( void )
{        
    int rec = 0;
    const bool ret = GetRecById< int, DummyLookup<int> >( rec, NULL );

    std::cout << "rec = " << rec << std::endl; // should be 123
} 


int main()
{                          
    testLookup();

    return 0;
}

The intention is that GetRecById() supports instantiation with different record queriying policies e.g. for unit testing purposes.

What am I doing wrong here? FWIW, it does compile under Sun Studio 10.

Thanks in advance.

Answer 1

The second parameter to GetRecById is a template, but you're trying to pass a type. You need:

GetRecById< int, DummyLookup >( rec, nullptr );
//                          ^ Note, no template argument here