unresolved external symbol when accessing a static variable

Question

class CommandManager {

public:
    void sendText(std::string command);
    static bool CommandManager::started;

private:


    bool parseCommand(std::string commands);

    void changeSpeed(std::vector<std::string> vec);
    void help(std::vector<std::string> vec);
};

And here's the client code:

CommandManager::started = true;

Linking these two files together I get:

1>UAlbertaBotModule.obj : error LNK2001: unresolved external symbol "public: static bool CommandManager::started" (?started@CommandManager@@2_NA)

1>C:\Development\School\cmput350-uofabot\UAlbertaBot\vs2008\Release\UAlbertaBot.dll : fatal error LNK1120: 1 unresolved externals

Where did I go wrong here?

possible duplicate of [Unresolved external symbol on static class members](http://stackoverflow.com/questions/195207/unresolved-external-symbol-on-static-class-members) — Joris Timmermans, Dec 05 '11 at 09:40
@KenLi: Try as I said in my answer. And let me know if you still face problem. — Nawaz, Dec 05 '11 at 09:53
@Nawaz It's working for me now, thanks for the help and the answer. — Ken Li, Dec 05 '11 at 09:57
@KenLi - the other question is about the *exact* same issue - you declared but did not define your static in your class. — Joris Timmermans, Dec 05 '11 at 10:27

score 24 · Accepted Answer · answered Dec 05 '11 at 09:42

You're doing that incorrectly.

class CommandManager {

public:
    void sendText(std::string command);
    static bool started; //NOT this -> bool CommandManager::started
    //...
};

then put the definition of static member in .cpp file as:

#include "CommandManager.h" //or whatever it is

bool CommandManager::started = true; //you must do this in .cpp file

Now you can use CommandManager::started in your client code.

score 4 · Answer 2 · answered Dec 05 '11 at 09:42

You should have inside your class:

class CommandManager {
 public:
  void sendText(std::string command);
  static bool started;
  //// etc
};

and outside your class, in a *.cc file (not in a *.hh header file), a definition like

bool CommandManager::started;

BTW, I believe you'll better make that private.

score 2 · Answer 3 · answered Dec 05 '11 at 09:41

2

Consider putting

bool CommandManager::started;

where you define other members.

answered Dec 05 '11 at 09:41

Michael Krelin - hacker

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unresolved external symbol when accessing a static variable

3 Answers3