How to add object in the static list on the constructor

Question

#include <forward_list>

using namespace std; 

class Test {
public:
    Test(){objects.push_front(this);}
private:
    static forward_list<Test*>objects; 
};

int main(){
    Test a; 
}//Visual Studio 17, error

Visual studio doesn't say what the problem is. It just retruns these two codes - LNK1120 and LNK2001.

Answer 1

You have an undefined reference to static forward_list<Test*>objects; You have to define your static object like this:

#include <forward_list>

using namespace std; 

class Test {
public:
    Test(){objects.push_front(this);}
private:
    static forward_list<Test*>objects; 
};

forward_list<Test*> Test::objects;

int main(){
    Test a; 
}//Visual Studio 17, error