"undefiniert Verweis auf" mit Singletons

Question

Mit dem folgenden Code:

class DBConnection 
{ 
// Methodes : private 
    private: 
     // Constructeur 
     DBConnection(); 

     // Destructeur 
     ~DBConnection(); 

// Methodes : public 
    public: 
     bool open(); 
     bool close(); 

// Methodes : public : static 
    public: 
     static DBConnection * getSingleton(); 

// Variables 
    private: 
     static DBConnection * singleton; 

     QSqlDatabase conn; 

     QString   driver, 
         host, 
         userName, 
         password, 
         DBName; 
}; 
#endif // DBCONNECTION_HPP 

---

#include "DBConnection.hpp" 

// Initialisation du singleton dans l'espace global, car static 
    DBConnection * DBConnection::singleton = 0; 

// Methodes : private 
    DBConnection::DBConnection() { 
     this->conn = QSqlDatabase::addDatabase("QMYSQL"); 
      this->conn.setHostName(""); 
      this->conn.setUserName(""); 
      this->conn.setPassword(""); 
      this->conn.setDatabaseName(""); 
    } 

    DBConnection::~DBConnection(){}; 

// Methodes : public 
    bool DBConnection::open() { 
     bool rep = this->conn.isOpen()?true:this->conn.open(); 

     if(!rep) 
      QMessageBox::critical(0, "Erreur critique !", "Impossible d'ouvrir la base de données !"); 

     return rep; 
    } 

DBConnection * DBConnection::getSingleton() { 
     if(singleton == 0) 
      singleton = new DBConnection; 
     return singleton; 
    } 

---

#ifndef DAOMYSQLFACTORY_HPP 
#define DAOMYSQLFACTORY_HPP 

#include "InterfaceDAOFactory.hpp" 
#include "DAO.hpp" 

class DAOMySQLFactory : public InterfaceDAOFactory 
{ 
// Methodes : private 
    private: 
     // Constructeur 
     DAOMySQLFactory(); 

     // Destructeur 
     ~DAOMySQLFactory(); 
// Methodes : public : heritées 
    public: 
     DAO * getDAOClient(); 

     DAO * getDAOSite(); 

     DAO * getDAOMachine(); 

// Methode : static 
    public: 
     static DAOMySQLFactory * getSingleton(); 

// Variables 
    private: 
     // Instance unique 
     static DAOMySQLFactory * singletonMySQLFactory; 
}; 

#endif // DAOMYSQLFACTORY_HPP 

---

#include "DAOMySQLFactory.hpp" 
#include "DBConnection.hpp" 
#include "DAOMySQLClient.hpp" 


DAOMySQLFactory * DAOMySQLFactory::singletonMySQLFactory = 0; 

// Methodes : private 
    // Constructeur 
    DAOMySQLFactory::DAOMySQLFactory() {} 
    // Destructeur 
    DAOMySQLFactory::~DAOMySQLFactory() {} 

// Methode : static 
    DAOMySQLFactory * DAOMySQLFactory::getSingleton() { 
     if(singletonMySQLFactory == 0) 
      singletonMySQLFactory = new DAOMySQLFactory; 
     return singletonMySQLFactory; 
    } 

// Methodes : public : heritee 

    DAO * DAOMySQLFactory::getDAOClient() { 
     return 0; 
    } 
... 

---

#include <QApplication> 

#include "WinMain.h" 

//TEST 
#include "DAOPersistenceFactory.hpp" 
#include "DAO.hpp" 
#include "DAOMySQLFactory.hpp" 
#include "DBConnection.hpp" 

int main(int argc, char *argv[]) 
{ 
    QApplication app(argc, argv); 

//TEST 
    InterfaceDAOFactory * idao = DAOPersistenceFactory::getDAOFactory(DAOPersistenceFactory::MySQL); 
    DAO * d = idao->getDAOClient(); 
    DBConnection::getSingleton(); 


    WinMain fen; 
    fen.show(); 

    return app.exec(); 
} 

---

#ifndef DAO_HPP 
#define DAO_HPP 

#include <QString> 
#include <QStringList> 
#include <QSqlQuery> 

class DAO { 
// Methodes : public 
    public: 
     DAO(); 
     virtual ~DAO(); 

// Methodes : public : abstraites 
    public: 
     virtual QStringList findAll() = 0; 

// Variable 
    protected: 
     QSqlQuery allQuery; 
}; 

#endif // DAO_HPP 

---

#include "DAO.hpp" 

DAO::DAO() {} 

DAO::~DAO(){} 

---

#ifndef DAOMYSQLCLIENT_HPP 
#define DAOMYSQLCLIENT_HPP 

#include <QString> 
#include <QStringList> 
#include <QSqlQuery> 

#include "DAO.hpp" 
#include "DBConnection.hpp" 

class DAOMySQLClient : public DAO 
{ 

// Methodes : public 
    public: 
     DAOMySQLClient(); 
    // DAOMySQLClient(DBConnection * connection); 
//Variables 
    private: 
     DBConnection * conn; 

     QSqlQuery  byIdQuery, 
         byNameQuery; 
}; 

#endif // DAOMYSQLCLIENT_HPP 

---

#include <QMessageBox> 
#include <QSqlError> 
#include <QVariant> 

#include "DAOMySQLClient.hpp" 


// Methodes : public 
    // Constructeur 
    DAOMySQLClient::DAOMySQLClient() {} 

    // Constructeur 
// DAOMySQLClient::DAOMySQLClient(DBConnection * connection) { 
//  this->conn = connection; 
//  this->conn->open(); 
//  initQueries(); 
// } 

... 

---

Warum ich habe eine

undefined reference to 'DBConnection::getSingleton()' 
collect2:ld returned 1 exit status 

in main() und DAOPersistenceFactory::getDAOFactory(DAOPersistenceFactory::MySQL); nicht während es scheint, die gleiche Implementierung zu haben?

Answer 1

Ich habe das Gefühl, dass Sie DBConnection.cpp auf Ihre .pro Datei hinzuzufügen vergessen. Wenn dies der Fall ist, versuchen Sie erneut, qmake auszuführen. Versuchen Sie auch, make clean.

Ich hatte viele seltsame Probleme mit veralteten Objektdateien in der Vergangenheit. ;)