Question

So I have this problem.

Basicly I have a templated interface:

template <typename T, typename U>
class                    Iinterface
{
 public:
 virtual ~Iinterface()
 // A pure methode for the example that gives me the problem
 virtual std::vector<T>        myMethod(T, U) = 0;
};

No problem for now.
So I declare a class that will inherit from this interface.

class                  firstclass : public Iinterface<std::string, int>
{
  // content doesnt matter. The problem is in second class inheritance.
  // here I just put the class so we can see how I inherited in 1st class.
};

Now the myMethod decleration in the cpp file.

template <>
std::vector<std::string>        firstClass::iInterface<std::string, int>::myMethod(std::string a, int b)
 {
      // methods code
 }

So far I have no problem. It is in my second class where I declare the myMethod function and that the type T is the same as the return value that it gives me a compilation error.

class                           secondClass : public IInterface<std::vector<std::string>, int>
{
  // class content
};

For the moment it compiles but when I declare the myMethod like this :

template <>
std::vector<std::string>                     secondClass::Iinterface<std::vector<std::string> a, int n>
{
  // methodes code
}

Here I get an error fot the std::vector return value and the one in the methods argument.
I believe it is a template conflict but I really don’t see how to go around this.

First error:

28 :template-id ‘_out<>’ for ‘std::vector<std::basic_string<char> > Iio<std::vector<std::basic_string<char> >, int>::_out(std::vector<std::basic_string<char> >, int)’ does not match any template declaration

Second error:

28 note: saw 1 ‘template<>’, need 2 for specializing a member function template

I am still learning how to code in c++ and learn fast but once in a while I get stuck and need some help.
Is the way I am trying to do this wrong?
Do I need to declare a third typename to go around this conflict? (I was thinking it will give just an other conflict because the two typenmaes are of the same type).

I know what I am trying to do might not be the best way to do this but I am still learning.

I tryed to make example code as simple as possible to explain my problem if you need more details dont hesitate to ask.

All help will be very apriciated.
Thanks.

Answer 1

It seems that return value for the second class function overload should be:

std::vector<std::vector<std::string> >

What compiler are you using, gcc gave error at template specifications.