Qt application with QSqlDatabase does not work properly when building it with macdeployqt

Question

In my application I am using a QSqlDatabase to store some information. I did built it successfully with the following command (no errors even with verbose=3):

macdeployqt AppName.app/ -dmg -qmldir=~/dev/AppName/qml

Before that I successfully installed mysql55 using port

sudo port install mysql55

If I try to run my application it does not crash, but it also does not anything which involves database access.

This is my code for opening a database etc:

#include <QSqlQuery>
#include <QSqlDriver>

const QString DATABASE_NAME = "com.company.program.db";

MyClass::MyClass(QObject *parent) : QObject(parent) {
    mDB = QSqlDatabase::addDatabase("QSQLITE");

    #ifdef Q_OS_LINUX
    QString path(QDir::home().path());
    path.append(QDir::separator()).append(DATABASE_NAME);
    path = QDir::toNativeSeparators(path);
    mDB.setDatabaseName(path);           // NOTE: We have to store database file into user home folder in Linux
    #else
    mDB.setDatabaseName(DATABASE_NAME);  // NOTE: File exists in the application private folder, in Symbian Qt implementation
    #endif

    bool notOpened = !mDB.open();

    QMessageBox::critical(0, "MyClass", mDB.lastError().databaseText()); // always is 'out of memory'

    if (notOpened) emit failedToOpen();
    else {
        // some initialization
    }
}

MyClass::~MyClass() {
    mDB.close();
}

Has anyone experienced the same issues / a fix for this one?

Note: I am using Mac OS X 10.9 and Qt5.3.2

after open is failed, try to get and check the error message by calling mDB->lastError()->databaseText() — Max Go
– Max Go, Commented Oct 2, 2014 at 8:46
Get the error message just after if (!mDB.open()) in the code — Max Go
– Max Go, Commented Oct 2, 2014 at 9:20
@N1ghtLight I get 'out of memory' exception. How can this happen? I have got only 2 tables, which do not have any entries at the beginning. — Niklas
– Niklas, Commented Oct 6, 2014 at 7:06
Niklas, search engine should be your best friend ... stackoverflow.com/a/18325616/2266412 — Max Go
– Max Go, Commented Oct 6, 2014 at 7:10

Valentin H · Accepted Answer · 2014-10-02 12:07:32Z

0

The Database Drivers are loaded at run-time. You won't get any database-config related errors during the compilation process, if the db-driver paths' are not correct. The paths' can't even be incorrect, as you build on a machine where Qt is installed.

On Windows this occurs often, when the exe can't access files in plugins\sqldrivers. Is there something like Linux's 'strace' on MAC? If yes, you could trace, in which paths your exe attempts to find driver plugins.

I always copy the entire plugin directory in installer and deploy it in the root-directory of the executable e.g. C:\Program Files (x86)\\plugins

Hope it helps.

answered Oct 2, 2014 at 12:07

Valentin H

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1 Comment

Niklas Over a year ago

I am on OS X and macdeployqt is doing all the stuff like copying the right directories ;)

Niklas · Accepted Answer · 2014-10-06 11:01:10Z

0

I managed to fix the out of memory error by executing this code:

#ifdef Q_OS_MAC
    QString databaseName = QApplication::applicationDirPath().append("/").append(DATABASE_NAME);
    mDB.setDatabaseName(databaseName);
#endif

answered Oct 6, 2014 at 11:01

Niklas

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