Qt Creator ComboBox crashes everytime and doesn't display a drop down menu

[Faris Elbaz]

Everytime i try to connect to my SQL server to populate a Combobox the box and any other drop down widget no longer "drops down". This is the code im using

void mainwin::populateTableComboBox() {
    SqlFunc sqlFunc;
    QSqlDatabase db = sqlFunc.getDatabase();

    if (db.isOpen()) {
        QSqlQuery query(db);
        query.exec("SELECT name FROM sys.tables WHERE type = 'U'");

        combobox->clear();
        while (query.next()) {
            combobox->addItem(query.value(0).toString());
        }
    } else {
        qDebug() << "Failed to open the SQL Server connection.";
    }
}

The second i run this code and this code only it breaks Combobox for the whole project and i need to create a new one, i've done this 6 times until now.

[Axel Spoerl]

@Faris-Elbaz
If we are talking a QComboBox, this code can’t break it.
What exactly happens, how and when?

[JonB]

@Faris-Elbaz
Start by replacing combobox->addItem(query.value(0).toString()); by qDebug() << query.value(0).toString(); and see how your program goes. Also check the return result from the exec(). And try combobox->addItem("Hello"); instead of yours.

[Faris Elbaz]

@Axel-Spoerl basically when i run this exact line of code, the combo box stops displaying a drop down menu entirely. I've made multiple new projects to narrow it down and it only happens whenever populateTableComboBox (the code i wrote above) runs. And even when i comment it out or remove it from the code entirely, no matter how many new ui files i make the combobox does not work correctly

[JonB]

@Faris-Elbaz
You want to start by isolating whether the issue lies in reading from the database or adding items to a combobox. If you try carefully each of my suggestions in reply above you should discover where the problem manifests.

[Faris Elbaz]

@JonB Hi, so i tried replacing the line with

qDebug() << query.value(0).toString(); <

The issue is not that my code doesn't run or that it doesn't open/build the application, the problem is that when i do build the application the drop down menu itself doesn't work.
@Axel-Spoerl
i only have a limited amount of times i can post per 5 minutes so here is some additional information, QODBC does not work for me. Im on macbook running my SQL server through docker to azure data studio, when i try to connect to the server using QODBC it doesn't work and i have to use a normal ODBC connection string to connect to it like this

bool SqlFunc::connOpen() {
    // Allocate the environment handle
    SQLAllocHandle(SQL_HANDLE_ENV, SQL_NULL_HANDLE, &henv);
    SQLSetEnvAttr(henv, SQL_ATTR_ODBC_VERSION, (SQLPOINTER)SQL_OV_ODBC3, 0);

    // Allocate the connection handle
    SQLAllocHandle(SQL_HANDLE_DBC, henv, &hdbc);

    // Connection string
    // Replace the connection string with your actual connection details
    SQLCHAR* connectionString = (SQLCHAR*)"DRIVER={ODBC Driver 18 for SQL Server};SERVER=localhost;SqlFunc=HospitalDS;UID=sa;PWD=reallyStrongPwd123;Encrypt=no";

    // Connect to the SQL Server
    SQLRETURN ret = SQLDriverConnect(hdbc, NULL, connectionString, SQL_NTS, NULL, 0, NULL, SQL_DRIVER_COMPLETE);

    return ret == SQL_SUCCESS || ret == SQL_SUCCESS_WITH_INFO;
}

void SqlFunc::connClose() {
    if (hdbc!= nullptr) {
        SQLDisconnect(hdbc);
        SQLFreeHandle(SQL_HANDLE_DBC, hdbc);
    }
    if (henv!= nullptr) {
        SQLFreeHandle(SQL_HANDLE_ENV, henv);
    }
}

From all the debugging and analysis i've been doing over the past 2-3 days I believe it has something to do with that and that also somehow the query is executing at the same time as the designer causing errors. This is just my theory.

[jsulm]

@Faris-Elbaz said in Qt Creator ComboBox crashes everytime and doesn't display a drop down menu:

The issue is not that my code doesn't run or that it doesn't open/build the application

This is not what @JonB was suggesting. He suggested to do some debugging to see where the issue is. Why don't you follow his suggestions?