Qt signal not working when passing pointer to a struct

Question

I have a Qt form that emits a signal; the signal passes a pointer to a structure which contains a load of data that the main window then sends out of my qextserialport.

This was working, but I have done something [unknown] and now when I connect the signal to a slot, unless I change it so that the singal does not pass anything, the connection to the signal will not work.

In mainwindow.cpp I have this:

void MainWindow::qt1245ValuesReceivedFromKeypad(char *dataPtr)
{

    bool connected;

    qt1245Window = new qt1245(this);
    connected = connect(qt1245Window,SIGNAL(sendMessageToKeypad(struct qt1245MessageStruct *qm)),this,SLOT(sendToQT1245(struct qt1245MessageStruct *qm)));
    qt1245Window->setupDataFromKeypad(dataPtr);
    qt1245Window->keyMapping(BinData);
    qt1245Window->keyDropDownChanged("DIM");       
 //   connected = connect(qt1245Window,SIGNAL(sendMessageToKeypad()),this,SLOT(sendToQT1245()));
    qt1245Window->exec();        
}

If I uncomment the second connect, and comment the first, and change the appropriate code, the connect works.

The structure is defined thus:

struct qt1245MessageStruct
{

    quint8 *dataPtr;
    quint8 length;
    quint8 keypadStartAddress;
    quint8 programType;

};

In qt1245.h I have this as part of the class declaration:

signals:
    void sendMessageToKeypad(struct qt1245MessageStruct *qm);

in qt1245.cpp. the signal is emitted as follows:

void qt1245::sendQT1245Message(qt1245MessageStruct *qm)
{

    emit sendMessageToKeypad(qm);

}

Can anyone shed any light on why connect returns false if I try to pass the pointer to the structure please? Also, is there away of making Qt give information as to why the connect fails, rather than just saying it has ?

If you need any more information, I will post it. I'm not sure at this juncture what would assist.

FWIW I'm on Linux, Qt Creator 4.9.0 based on Qt 5.12.2.

Answer 1

The parameters in the connect call are wrong.

connect(qt1245Window,
        SIGNAL(sendMessageToKeypad(struct qt1245MessageStruct*qm)),
        this,
        SLOT(sendToQT1245(struct qt1245MessageStruct *qm)));

The name of the parameter does not go into the SIGNAL and SLOT macros. The correct syntax is:

connect(qt1245Window,
        SIGNAL(sendMessageToKeypad(struct qt1245MessageStruct*)),
        this,
        SLOT(sendToQT1245(struct qt1245MessageStruct *)));