[solved] Application crash QSqlQuery(dbconnection) is called.

David.G

At first sight...

In database.h you don't include QSqlDatabase or have a forward declaration for it. I'm going to assume you've added QT += sql in your .pro for it to compile . Usually if you press F5 QtCreator will show you the lines where it stopped at. (not a silver bullet, but at the very least it will give you an idea. (it can be messy).).

SGaist

Hi,

Are you sure you are not accessing an uninitialized variable ? You use model in several function as local variable, does it shadow a class member ?

sachi

dbCon is initialized. if i use dbCon any function other than createmodel aplication crashed. I cant figure out whats wrong.

sachi

I found where i was wrong. I haven't initilized database object where this fuction was called. but right now dbCon is closed. i have open connection using dbCon.open(). but still dbCon.isOpen returns false.

SGaist

Is dbCon correctly configured before calling open ? What does lastError return ?

sachi

yes. database is configured correctly. i have created tablemodel and do the insert, edit etc. but in other functions it shows database is not open. lastError returns "driver not loaded". I am using "QMYSQL" driver. i chekced the output of QSqlDatabase::drivers(). It returns "QSQLITE", "QMYSQL", "QMYSQL3", "QPSQL", "QPSQL7".

here is my two functions
// Record login and logouts
bool Database::AddLoginRecord(int usrID, int islogin) {
QSqlQuery * query = new QSqlQuery(dbCon);
// msg->Error(query->lastError());
qDebug() << QSqlDatabase::drivers();
query->prepare("INSERT INTO login_session VaLUES (NULL,?,?)");
query->addBindValue(usrID);
query->addBindValue(islogin);

return query->exec();

}

// Create table model for given table
QSqlTableModel * Database::CreateModel(QString table) {
QSqlTableModel * model = new QSqlTableModel(0,dbCon);
model->setTable('' + table + '');
return model;
}

create model function works fine and i can accesse database. but when addLoginRecord called i got the error "database not open"

sachi

I just found problem is not with database class. it is with mainWindow class. if I create object using database class in mainWindow and called method from database.cpp. database connection show as invaild.

SGaist

Driver not loaded ? Do you have MySQL installed properly ?

sachi

yeah i have solved problem. its was at the main function. i have created database connection after the MainWindow is created. so mainWindow cannot use the database connection. By the way thanks for your help guys.

SGaist

Thanks for sharing your solution !

Since you have it working now, please update the thread title prepending [solved] so other forum users may know a solution has been found :)