c++ - 如何重载和调用先前在其基类中定义的派生类中的方法？

Question

这是基类：

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

这是派生类：

#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
}

给定的错误是：

第 29 行：IntelliSense：不存在从“std::pair”到“long double”的合适转换函数

第 29 行：IntelliSense：函数调用中的参数太少

显然，问题是我无法从派生类访问基类中的方法，即使它是公共定义的。

如何使此代码工作？

（我的 IDE 是 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

为了调用超类方法 write ::AddData(x, y);。新Plotter::AddData方法使DataLogger::AddData 隐形。

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));
}