初始化类型为vector的静态类成员

Question

I have a class with a private static instance variable of type vector >. I had a strategy for initialising this variable that involved passing a temporary array to a function that was not a class member. This worked on older versions of g++, but not with g++ 4.8.2.

Here's what I'm doing:

initclass.cpp:

#include "initclass.h"

#define NINT 5

vector<pair<int,int> > initInstance(const pair<int,int> *array, int nint)
{
  vector<pair<int,int> > vect;
  vect.assign(array, array + nint);

  return vect;
}

const vector<pair<int,int> > initclass::_intvect = 
  initInstance((pair<int,int>[NINT]){pair<int,int>(1,2), pair<int,int>(3,4), 
                                     pair<int,int>(5,6), pair<int,int>(7,8), 
                                     pair<int,int>(9,10)}, 
    NINT);

initclass.h:

#ifndef INITCLASS_H_
#define INITCLASS_H_

#include <utility>
#include <vector>
using namespace std;

class initclass
{
public:      
  static const vector<pair<int,int> > & intvect() { return _intvect; };

private:
  const static vector<pair<int,int> > _intvect;      
};

#endif

I can make this work by just declaring the array of pair objects before calling the initInstance function, but I'm wondering if there's a better way (this is of course a simplified example of what I'm trying to do: in my real code, there are many calls to the initialisation function with many arrays, and I'd rather not declare each of them prior to each function call).

EDIT: I thought briefly I'd found a solution here: Using array init list as temporary in C++11?

The second answer has a conversion from a const array to a (non-const) pointer. In my case this would change the initInstance function call to:

const vector<pair<int,int> > initclass::_intvect = initInstance((pair<int,int>*)(const pair<int,int> []){pair<int,int>(1,2), pair<int,int>(3,4), pair<int,int>(5,6), pair<int,int>(7,8), pair<int,int>(9,10)}, NINT);

This compiles, but the initInstance function never gets called, for some reason.

Answer 1

Yes, there is a better way. You can remove that awful function, which does nothing useful. You can initialize vector like this :

#include <iostream>
#include <vector>
#include <utility>




struct A
{
    const static std::vector<std::pair<int,int> > intvect;
};

const std::vector<std::pair<int,int> > A::intvect{ std::pair<int,int>(1,2), std::pair<int,int>(3,4), 
                                                   std::pair<int,int>(5,6), std::pair<int,int>(7,8), 
                                                   std::pair<int,int>(9,10) };

int main()
{
    (void) A::intvect;
}

This is using the c++11 7th constructor of vector - the one with taking initializer list.