What i am trying to do is to make a dialog where the user enters the data needed for a connection and finally makes the connection.

I have two buttons.

The first button should check whether a connection has already been made and if not start a new connection. If a connection has already been made then write a message saying connection already open.

The second button should disconnect the database.

The problem is that I cannot disconnect the database and that instead of checking whether one is already open it creates another one each time i ress the button. (and I receive the relevant error code form the command line).

I have attached the code. I cant figure out what's wrong on my own.Your help is much appreciated.

Many thanks in advance.

Qt Code: 
  1. #include "database.h"
  2.  
  3. #include <QtGui>
  4. #include <QApplication>
  5.  
  6. int main(int argc, char *argv[])
  7. {
  8.     QApplication a(argc, argv);
  9.     database w;
  10.     w.show();
  11.     return a.exec();
  12. }
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Qt Code: 
  1. #ifndef DATABASE_H
  2. #define DATABASE_H
  3.  
  4. #include <QtGui/QWidget>
  5. #include <QtSql>
  6. #include "ui_database.h"
  7. class A {
  8. 	public:
  9. 	QString pinakas;
  10. 	QString onoma;
  11. 	QString kodikos;
  12. };
  13.  
  14. class database : public QWidget
  15. {
  16.     Q_OBJECT
  17.  
  18. public:
  19.     database(QWidget *parent = 0);
  20.     ~database();
  21.  
  22.  
  23. public slots:
  24. 	void sindesou();
  25. 	void aposindesou();
  26.  
  27. private:
  28.     Ui::databaseClass ui;
  29.     A ena;
  31.  
  32. };
  33.  
  34. #endif // DATABASE_H
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database.cpp:
Qt Code: 
  1. #include "database.h"
  2. #include <QtSql>
  3. #include <QMessageBox>
  4. #include <QSqlDatabase>
  5. #include <QSqlError>
  6. #include <QSqlQuery>
  7. #include <QApplication>
  8. #include <QCoreApplication>
  9. #include <QDebug> 
  10. #include "ui_database.h"
  11.  
  12.  
  13.  
  14. database::database(QWidget *parent)
  15.     : QWidget(parent)
  16. {
  17. 	ui.setupUi(this);
  18. 	connect(ui.sindesi, SIGNAL(clicked()), this, SLOT(sindesou()));
  19. 	connect(ui.aposindesi, SIGNAL(clicked()), this, SLOT(aposindesou()));
  20.  
  21. 	//QSqlDatabase db = QSqlDatabase::addDatabase("QMYSQL");
  22. }
  23.  
  24. void database::sindesou() {
  25. 	    ena.pinakas = ui.pinakas->text();
  26. 	    ena.onoma = ui.onoma->text();
  27. 	    ena.kodikos = ui.kodikos->text();
  28. 	    if (!db.open()) {
  29. 	    QSqlDatabase db = QSqlDatabase::addDatabase("QMYSQL");
  30. 	    db.setDatabaseName(ena.pinakas);
  31. 	    db.setUserName(ena.onoma); 
  32. 	    db.setPassword(ena.kodikos); 
  33. 	    db.setHostName("127.0.0.1");
  34. 	    db.setPort( 3306 );                     
  35. 	    if (!db.open()) {
  36. 	        ui.katastasi->setText("Not connected");
  37. 	    } else {
  38. 	    	ui.katastasi->setText("connected");
  39. 	    }
  40. 	    }
  41. 	    else {
  42. 	    	ui.katastasi->setText("It has already been connected");
  43. 	    }
  44. 	    };
  45.  
  46.  
  47. void database::aposindesou() {
  48. 	db.close();///<<--- This doesnt close the connection
  49. }
  50.  
  51. database::~database()
  52. {
  53.  
  54. }
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