I am trying to establish a database connection in Qt using OOP concepts. I have a separate databaseconnection class and databaseconnection header file.
#ifndef DATABASECONNECTION
#define DATABASECONNECTION
bool dbcon();
#endif // DATABASECONNECTION
This Login.h file
#include <QFileInfo>
namespace Ui {
class Login;
}
class Login : public QMainWindow
{
Q_OBJECT
public:
explicit Login(QWidget *parent = 0);
~Login();
private slots:
// void on_btnLogin_clicked();
void on_btnCancel_clicked();
void on_btnLog_clicked();
private:
Ui::Login *ui;
};
#endif // LOGIN_H
.This is my databaseconnection.cpp which implements the dbcon ().
#include <QtSql/QSqlDatabase>
#include <QtSql/QSqlDriver>
#include <QtSql/QSqlQuery>
#include <QDebug>
#include "databaseconnection.h"
DatabaseConection::DatabaseConection()
{
}
bool DatabaseConection :: dbCon()
{
QSqlDatabase db = QSqlDatabase :: addDatabase("QMSQL");
db.setHostName("localhost");
db.setDatabaseName("library");
db.setUserName("root");
db.setPassword("");
if(!db.open())
{
qDebug()<<"Database error occured";
return false;
}
else
return true;
}
I want to call this database connection method inside my MainWindow instead of implementing the connection within MainWindow. This is my MainWindow class.
#include <QtSql>
#include <QDebug>
#include <QFileInfo>
#include "login.h"
#include "databaseconection.h"
#include "ui_login.h"
Login::Login(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::Login)
{
ui->setupUi(this);
dbcon();
}
Login::~Login()
{
delete ui;
}
void Login::on_btnLog_clicked()
{
}
void Login::on_btnCancel_clicked()
{
}
Although I include all the header files It gives an error saying that dbcon() is out of scope. I don't have an idea how to inherit databaseconnection class in MainWindow class(MainWindow class is the login.cpp)
After performing some actions and trying to run the project this was shown. I can't figure out the reason for this. Please help me to figure out this. Thanks in advance
Starting H:\c++Prac\build-Libro-Desktop_Qt_5_5_1_MinGW_32bit-Debug\debug\Libro.exe...
The program has unexpectedly finished.
H:\c++Prac\build-Libro-Desktop_Qt_5_5_1_MinGW_32bit-Debug\debug\Libro.exe crashed
Your databaseconnection.h declares a standalone function dbcon()
but in the implementation file (the cpp) you're defining a class DatabaseConection of which dbcon()
is a method
You need to properly declare the DatabaseConnection class in the header (constructor etc.), then in MainWindow you can instantiate a class of that type and use the method.
You are doing it wrong. Try this
databaseconnection.h
#ifndef DATABASECONNECTION
#define DATABASECONNECTION
class DatabaseConnection
{
public:
DatabaseConnection() {}
bool dbcon() const;
};
#endif //DATABASECONNECTION
databaseconnection.cpp
bool DatabaseConnection::dbcon() const
{
QSqlDatabase db = QSqlDatabase :: addDatabase("QMSQL");
db.setHostName("localhost");
db.setDatabaseName("library");
db.setUserName("root");
db.setPassword("");
if(!db.open()) {
qDebug()<<"Database error occured";
return false;
} else {
return true;
}
}
Now, you have two options.
login.h
#include "databaseconnection.h"
class Login : public QMainWindow, public DatabaseConnection
{
Q_OBJECT
...
};
login.cpp
Login::Login(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::Login)
{
ui->setupUi(this);
dbcon();
}
login.h
#include "databaseconnection.h"
class Login : public QMainWindow
{
Q_OBJECT
...
private:
DatabaseConnection dbConnection;
};
login.cpp
Login::Login(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::Login),
dbConnection()
{
ui->setupUi(this);
dbConnection.dbcon();
}
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