Problems with Open-Source Downloads read https://www.qt.io/blog/problem-with-open-source-downloads and https://forum.qt.io/post/638946

QByteArray class input to function - pass by reference or pass by value???



  • When passing a QByteArray variable to a function, is the variable pass by reference or pass by value?

    I have the following code in my program:

    @
    // global variable
    QByteArray RX_Buffer;

    // In one of my function, I am passing RX_Buffer to a function
    bool ParseMessage (QByteArray data, QByteArray rx_data)
    {
    // state machine processing to populate values to rx_data
    for(int i = 0; i < 10; i++)
    rx_data[i] = (quint8)i;
    }
    bool cls_ElectricityMeter::ReadDemo()
    {
    ParseMessage(TX_Buffer, RX_Buffer);
    return false;
    }
    @

    At the return point of ReadDemo function, RX_Buffer.data() does not contain the populated values from ParseMessage. Am I doing something wrong?



  • If you want to change your method parameter you should pass it by reference (i.e. with &). In your case implicitly shared copy created at method call and after first assign sharing breaks.



  • sorry but I do not quite understand . Can you provide a code snippet?



  • nevermind... i got it!!! thanks a bundle. I assumed classes were pass by reference by default for some reason.


Log in to reply