c++11 static functional member variable - c++

Question

Well, I'm stumped. I've always had a bit of a hard time with static member variables and functions, so if the answer to this is really obvious, I apologize. I can't figure out what's wrong, though.
In WSGrid.h:
#include <functional>
class WSGrid
{
public:
//constructors...
static const std::function< char( void ) > _randomChar;
//private data...
};
In WSGrid.cpp:
#include <random>
std::default_random_engine generator;
std::uniform_int_distribution< char > distribution;
const WSGrid::_randomChar = std::bind( distribution, generator );
In my main.cpp:
#include "WSGrid.h"
#include <iostream>
int main( int argc, char* argv[] )
{
std::cout << WSGrid::_randomChar() << std::endl;
return 0;
}
And when I try to compile (g++ -std=c++11 -Wall -pedantic main.cpp), I get "undefined reference to WSGrid::_randomChar".
So... it looks, to me, like I'm doing everything right. I'm following the syntax found here, at least as far as I'm aware. But apparently there's something wrong.

Answer 1

You need to define _randomChar correctly.
update :
const WSGrid::_randomChar = std::bind( distribution, generator );
to:
const std::function<char(void)> WSGrid::_randomChar = std::bind(distribution, generator);
Also you need to link WSGrid.cpp
g++ -std=c++11 -Wall -pedantic -c WSGrid.cpp -o WSGrid.o
g++ -std=c++11 -Wall -pedantic main.cpp WSGrid.o