How to overload and call a method in a derived class which was previously defined in its base class?

Question

This is the base class:

template <class T>
class DataLogger
{
        // ...
    public:
        void AddData(T Data);
        // ...
}

And this is the derived class:

#include "DataLogger.h"
#include <utility>

class Plotter : public DataLogger<std::pair<long double, long double>>
{
        // ...
    public:
        void AddData(long double x, long double y);
        // ...
}

// This method is supposed to wrap the original AddData() method
// which was defined in the base class
void Plotter::AddData(long double x, long double y)
{
    AddData(std::make_pair(x, y));  // LINE #29
}

The given error is:

LINE 29: IntelliSense: no suitable conversion function from "std::pair" to "long double" exists

LINE 29: IntelliSense: too few arguments in function call

Apparently, the problem is that I can not access to the method in base class from derived class, even though it is defined public.

How do I make this code work?

(My IDE is Visual Studio 2010.)

Answer 1

Your AddData from the base is hidden by the AddData from derived class. Either explicitly qualify the call DataLogger<std::pair<long double, long double>>::AddData(...) or bring it to scope with using DataLogger<std::pair<long double, long double>>::AddData;

Answer 2

Your AddData in derived class hides the function AddData in the base class, so all you need to do is, unhide the latter using using directive:

class Plotter : public DataLogger<std::pair<long double, long double>>
{

public:
   //unhiding : bringing base class function into scope!
   using DataLogger<std::pair<long double, long double>>::AddData;

};

Read Item 33: Avoid hiding inherited names from Effective C++ by Scott Meyers.

Answer 3

In order to call the super class method write ::AddData(x, y);. The new Plotter::AddData method makes DataLogger::AddData invisible.

Answer 4

The problem is not "that I can not access to the method in base class from derived class, even though it is defined public".

The problem is that Plotter::AddData is trying to call itself (with a pair) instead of the AddData in the base class.

You can make the call explicit by writing

void Plotter::AddData(long double x, long double y)
{
    DataLogger<std::pair<long double, long double>>::AddData(std::make_pair(x, y));
}