c++ - Error: LNK2001: unresolved external symbol "private: static class -

this forum contains many examples of such situation, in case static variables defined correctly, still error. issue not duplicate of previous , above link not answer question. suggested 21 answers post not have solution simon gave me here, please unmark "duplicate".

seems i've declared correctly, check this:

.h file:

class valuesetsmodelscontainer : public qobject {   q_object  public:   static void dllexport loadallergiesvaluesets(mptdatabase *db);   static void dllexport loadproceduresvaluesets(mptdatabase *db);    // models access functions   static qstandarditemmodel *drugsmodel();   static qstandarditemmodel *substancemodel();   static qstandarditemmodel *reactionsmodel();  private:   static qstandarditemmodel *mydrugsmodel, *mysubstancemodel, *myreactionsmodel; }; 

.cpp:

qstandarditemmodel *valuesetsmodelscontainer::mydrugsmodel = 0; qstandarditemmodel *valuesetsmodelscontainer::mysubstancemodel = 0; qstandarditemmodel *valuesetsmodelscontainer::myreactionsmodel = 0;  qstandarditemmodel *valuesetsmodelscontainer::drugsmodel() {   return valuesetsmodelscontainer::mydrugsmodel; }  qstandarditemmodel *valuesetsmodelscontainer::substancemodel() {   return valuesetsmodelscontainer::mysubstancemodel; }  qstandarditemmodel *valuesetsmodelscontainer::reactionsmodel() {   return valuesetsmodelscontainer::myreactionsmodel; } 

so static variables defined in cpp, still linking error in module calls valuesetsmodelscontainer methods:

• allergiesdialog.obj:-1: error: lnk2001: unresolved external symbol "private: static class qstandarditemmodel * valuesetsmodelscontainer::mydrugsmodel" (?mydrugsmodel@valuesetsmodelscontainer@@0pavqstandarditemmodel@@a)
• allergiesdialog.obj:-1: error: lnk2001: unresolved external symbol "private: static class qstandarditemmodel *
  valuesetsmodelscontainer::mysubstancemodel"
  (?mysubstancemodel@valuesetsmodelscontainer@@0pavqstandarditemmodel@@a)
• allergiesdialog.obj:-1: error: lnk2001: unresolved external symbol "private: static class qstandarditemmodel *
  valuesetsmodelscontainer::myreactionsmodel"
  (?myreactionsmodel@valuesetsmodelscontainer@@0pavqstandarditemmodel@@a)

where problem be?

from link commands turned out linking objects dll , in second step link dll final binary. might caused subdirs template in project settings.

whenever want have method of dll available outside, need make available via __declspec( dllexport ). guess done in custom precompiler constant dllexport.

now try in .h file:

static dllexport qstandarditemmodel *drugsmodel(); static dllexport qstandarditemmodel *substancemodel(); static dllexport qstandarditemmodel *reactionsmodel(); 

to make methods available outside dll.

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by way: don't think makes sense here have intermediate dynamic library (dll) if linking stuff own project , don't need make available else. consider using static library instead setting template = lib , config += staticlib in .pro file valuesetsmodelscontainer in. topic , question.