How to solve compile error QObject::QObject(const QObject&)' is private Q_DISABLE_COPY(QObject)

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I'm trying to create a class in QT I gt this compile error
QObject::QObject(const QObject&)' is private Q_DISABLE_COPY(QObject)

Thanks to anyone who can help

Here is the header for my class connect2sql.h

C++

#ifndef CONNECT2SQL_H
#define CONNECT2SQL_H


#include <QApplication>
#include <QDebug>
#include <QString>
#include <QtSql/QSql>
#include <QtSql/QSqlDatabase>
#include <QtSql/QSqlQuery>
#include <QtSql/QSqlError>
#include <QMessageBox>
#include "Globals.h"

//class connect2SQL : public QWidget
namespace grillot {
class connect2SQL;
}
class connect2SQL : public QObject
{
    Q_OBJECT


public:


    connect2SQL(QObject *parent = 0);
    void TryConnect();

    ~connect2SQL();

QString Server;
QString User;
QString Password;
QString Catalog;
bool isConnected;


signals:

public slots:

//void TryConnect();




protected:


private:
    connect2SQL *mconnect2SQL;
    QString m_Server;
    QString m_User;
    QString m_Password;
    QString m_Catalog;
    QSqlDatabase db;
};

#endif // CONNECT2SQL_H

Here is the implementation connect2sql.cpp

#include "connect2sql.h"


connect2SQL::connect2SQL(QObject *parent=0) :
QWidget(parent)
{

void connect2SQL::TryConnect()
{
    //QSqlDatabase db;
    qDebug() << "inside connect2SQL::TryConnect";
    db = QSqlDatabase::addDatabase("QMYSQL");

    QString m_server;
    QString m_user;
    QString m_pwd;

    db.setHostName(m_Server);

    db.setDatabaseName(m_Catalog);
    db.setUserName(m_User);
    db.setPassword(m_Password);

      if (!db.open()) {
          isConnected = false;
      }
      else
          isConnected = true


}
 connect2SQL::~TryConnect()
 {
     db.close;

 }

Here is code where I try to use this class

connect2SQL mconnect2SQL = new connect2SQL(this);
    mconnect2SQL.server="localhost";
    mconnect2SQL.user ="root";
    mconnect2SQL.pwd ="moonpie".
    mconnect2SQL.catalog="mydb";
    mconnect2SQL.TryConnect();

      if (!mconnect2SQL.isConnected()) 

{ ....}

when I double click on the error it goes to this code in object.h

Q_DISABLE_COPY(QObject)

I've tried inheirting from QWidget and get the same error

Posted 11-Dec-15 7:55am

JohnnyG62

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2 solutions

Solution 1

This is behaviour by design. As I understand it, you must implement a own copy constructor with pointer syntax.

BTW: you could found this information by Google ;-)

Posted 13-Dec-15 20:57pm

KarstenK

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Jochen Arndt · Accepted Answer · 2015-12-13T22:35:00

There are two errors (at least) in your code snippets:

Your connect2SQL class is declared based on QObject:

C++

class connect2SQL : public QObject

But in the constructor you are calling the QWidget constructor:

C++

connect2SQL::connect2SQL(QObject *parent=0) :
QWidget(parent)
{
// ...
};

The new operator returns an address to an allocated object. So this line should result in a compiler error like "conversion from 'connect2SQL*' to non-scalar type 'connect2SQL' requested":

connect2SQL mconnect2SQL = new connect2SQL(this);

Instead it must be a pointer:

connect2SQL *mconnect2SQL = new connect2SQL(this);
mconnect2SQL->server="localhost";
// ...