"Undefined symbols" with static fields

xalisonx

Hi guys!

With this code:

#include <QString>
#include <QDir>

class Repository
{
public:
    static void Create() {
        BaseDirectory = Require("/Library/Application Support/myapp");
        LogDirectory = Require(BaseDirectory, "Logs");
    }
    static QString GetBaseDirectory() {
        return BaseDirectory;
    }
private:
    static QString BaseDirectory;
    static QString LogDirectory;

    static QString Require(QString path){
        QDir dir(path);
        if (!dir.exists(path)) {
            dir.mkpath(path);
        }
        return path;
    }
    static QString Require(QString basePath, QString relPath){
        QString path = basePath + QDir::separator() + relPath;
        Require(path);
        return path;
    }
};

used here:

#include "Repository.h"
int main(int argc, char *argv[])
{    
   Repository::Create();
}

i get this linker error:

Undefined symbols for architecture x86_64:
  "Repository::LogDirectory", referenced from:
      Repository::Create() in main.o
  "Repository::BaseDirectory", referenced from:
      Repository::Create() in main.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

Clang on MAC!
What's the problem??????
:-(

mcosta

You forgot to define the static members.
Something like

QString Repository::BaseDirectory;
QString Repository::LogDirectory;

in cpp file

xalisonx

woah you have saved my day!!!

xalisonx

@mcosta is possible to define the static members in .h file?

mcosta

You have to be sure that static objects are initialized once. If you include into header file they will be initialized every time you include the header file. You can do this using special include guards but IMO is a very bad code style.

I suggest to create a cpp file (or you can do it in main.cpp)