Call Base Default constructor Template Class [duplicate]

Question

This question already has answers here:

Why can templates only be implemented in the header file? (17 answers)

Closed 8 years ago.

The question is how to call the base constructor from an inherited template class. I want to create a FixedQueue and overload some function in std::queue. Therefore std:queue is the base class. The keyword using, since c++11, can be used to call the base and it works if this is a specialised class, but I cannot get it working with a template class.

Furthermore I tried it to use the old c++ standard in which I simply invoke the defined constructors in std::queue. However it doesn't work.

h file

#ifndef _HEADER_FIXED_QUEUE_
#define _HEADER_FIXED_QUEUE_

#include <queue>
#include <iostream>

template<class T> 
class FixedQueue : public std::queue<T>
{
  //using queue<T>::queue<T>;

  public:
    FixedQueue();
    FixedQueue(const T &initial_var);
    void foo() { std::cout << "inside\n"; }

};

#endif

cpp file

#include "FixedQueue.h"

template<typename T>
FixedQueue<T>::FixedQueue()
:
  std::queue<T>()
{ 
  std::cout << "Default Constructor FixedQueue\n";
}

template<typename T>
FixedQueue<T>::FixedQueue(const T &initial_var)
:
  std::queue<T>(initial_var)
{ 
  std::cout << "Specialized Constructor FixedQueue\n";
}

main file.

#include <iostream>
#include "FixedQueue.h"

int main()
{
  FixedQueue<int> d_frameSlices;


  std::cout << "I want to do something with my queue\n";
}

The question is thus. How do I chain the constructors to the defined constructors in the base class std::queue. The template thing is killing me.

This is the error message I obtain from clang, which is the usual undefined reference.

Undefined symbols for architecture x86_64:
  "FixedQueue<int>::FixedQueue()", referenced from:
      _main in main-lqoFSA.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

If someone knows how to do this with "using" or the old fashion way I am happy with both. Thanks in advance

Answer 1

you should not put the template in cpp file put it all in header file