Unresolved external symbol C++

Question

I ahve a problem with a code below: ProgrammSettings.h ``` #pragma once static class ProgrammSettings { public: static int fd; }; ``` Settings.cpp ``` #include "ProgrammSettings.h" static bool LoadSettings() { ProgrammSettings::fd = 2; // here error Unresolved symbol!! return true; } ``` What i'm doing wrong? Thanks!

Accepted Answer

Unlike instance variables that require only a declaration, static member variabs of the class must also be defined.

Currently, your code contains only a declaration. Add a definition of your static `fd` variable to a cpp file to fix the error:

```
int ProgrammSettings::fd;
```

Unresolved external symbol C++

Solution

Problem