static variable link error [duplicate]
You must define the statics in the cpp file.
Log.cpp
#include "Log.h"#include <ostream>string Log::theString; // <---- define static herevoid Log::method(string arg){ theString = "hola"; cout << theString << endl; }You should also remove using namespace std; from the header. Get into the habit while you still can. This will pollute the global namespace with std wherever you include the header.
You declared static string theString;, but haven't defined it.
Include
string Log::theString;to your cpp file