Have not read the book yet. I just want to try if every code is working before reading the book.
Turns out i got 2 unresolved externals.
Here are they
Error 2 error LNK2019: unresolved external symbol "class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > __cdecl toString<__int64>(__int64 const &)" (??$toString@_J@@YA?AV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@AB_J@Z) referenced in function "private: void __thiscall Game::updateStatistics(class sf::Time)"
Error 1 error LNK2019: unresolved external symbol "class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > __cdecl toString<unsigned int>(unsigned int const &)" (??$toString@I@@YA?AV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@ABI@Z) referenced in function "private: void __thiscall Game::updateStatistics(class sf::Time)"