same signal-slot connection in two windows

russjohn834

This is how I make the connection in Settings.

Settings::Settings(QString patientLabel, QWidget *parent) : QMainWindow(parent)
    , ui(new Ui::Settings)
{
    ui->setupUi(this);
   
    connect(&api, &tetra_grip_api::tetraGripEvent,this, &Settings::eventHandler);
}

Connection is successfull (qDebug()<<connect(....) gives TRUE) also the a QLabel and an LED in the eventHandler slot works perfectly.

In the same way I try to connect in the Patients:

Patients::Patients(QWidget *parent) : QMainWindow(parent)
    , ui(new Ui::Patients)
{
    ui->setupUi(this);
   
    connect(&api, &tetra_grip_api::tetraGripEvent,this, &Patients::eventHandlerTwo);
}

here connection is successfull (qDebug()<<connect(....) gives TRUE) but the a QLabel and an LED in the eventHandlerTwo are not working.

JonB

@russjohn834
How do I know &api refers to the same, global, initialized api instance in both cases?
And I see nothing in code about any QLabel in either case, not mentioned by you before...
You have to supply the necessary/relevant code if you want people to help.
Use a debugger to make sure whether slots are being hit.

russjohn834

@JonB

I thought api should be known and accessible to all classes if intialized as global in the main.cpp

#include <QApplication>

tetra_grip_api api; //-------------> api instance

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    api.openSerialPort();
    QObject::connect(api.serial, SIGNAL(readyRead()), &api, SLOT(readData()));
    QObject::connect(api.serial, SIGNAL(error(QSerialPort::SerialPortError)),&api, SLOT(ErrorHandler(QSerialPort::SerialPortError))); // error handling


    Settings w(nullptr);
    w.show();

    return a.exec();
}

Correct me if I'm wrong.

JonB

@russjohn834
Your Settings & Patients classes are defined in a different source module from main.cpp, right? So how do they gain access to reference the api symbol in order to compile?

 connect(&api, &tetra_grip_api::tetraGripEvent,this, &Patients::eventHandlerTwo);

I am having to tease out each bit of relevant information, one at a time....

russjohn834

@JonB
Correct. I actually did not do anything other that making apiinstance as global in main.cpp. That might be the issue. But dont know how to proceed. How do I make Patients classes know about global api instance?

jsulm

@russjohn834 You should avoid global variables as much as possible.
Just pass the pointer to api to Settings & Patients constructors...

jazzco2

Did you ensure that the connection in Patients is done before the signal tetra_grip_api::tetraGripEvent is emitted? Some qDebugs around connection, in the very first line of Patients::eventHandlerTwo and in the deconstructor of Patients should help to prove that.

JonB

@russjohn834 said in same signal-slot connection in two windows:

@JonB
Correct. I actually did not do anything other that making apiinstance as global in main.cpp. That might be the issue. But dont know how to proceed. How do I make Patients classes know about global api instance?

I truly, truly do not understand. You said your program runs but does/does not behave properly in the cases you mentioned. I asked how you can even compile your Settings/Patients modules/.cpp source files which contain the line connect(&api, ..., when api is defined in main.cpp? From what you have said/shown they should error at compile-time with a "No such variable: api" message. So I will leave others to help, who obviously understand your source code better than I.

jazzco2

@JonB Yes, that's interesting. You can't include main.cpp in Settings or in Patients. So main.cpps line

tetra_grip_api api; //-------------> api instance

isn't visible anywhere!

jazzco2

@russjohn834 If you are using QtCreator: When you go on the &api in your connect statements in both Settings and Patients and press F2 - where does it lead you to?

russjohn834

@jazzco2

From both Settings and Patients , &api leads me here:

#ifndef TETRA_GRIP_API_H
#define TETRA_GRIP_API_H

#include <QObject>
#include <stdio.h>
#include <stdlib.h>
#include <iostream>
#include <QLabel>
#include <QMessageBox>
#include <QTimer>

#define _CRT_SECURE_NO_DEPRECATE

class tetra_grip_api : public QObject
{
    Q_OBJECT

public:
    explicit tetra_grip_api(QObject *parent = nullptr);

    #define MAX_CONFIG_FILE_LENGTH (10000)

     void static send_config_file(QByteArray config, bool nonvolatile);
     void static send_long_register(uint8_t, uint32_t, uint8_t *);
     void static stimulation_set_current(unsigned int, unsigned int);

     QSerialPort *serial = nullptr;

     QTimer autoConnectionTimer;
     bool tryToAutoconnect;

signals:

     void tetraGripEvent(STIM_GUI_TOPIC_T topic, uint8_t reg, uint32_t value);



public slots:

     void openSerialPort();
     void closeSerialPort();
     void readData();


private slots:

     void ErrorHandler(QSerialPort::SerialPortError error);

private:

        QString comPortName;

};

extern tetra_grip_api api;  //----------> it leads me here

#endif // TETRA_GRIP_API_H

jsulm

@russjohn834 said in same signal-slot connection in two windows:

extern tetra_grip_api api;

You really should not do it like this. Pass pointer to the constructors of the classes which need it.

JonB

@jazzco2 said in same signal-slot connection in two windows:

@JonB Yes, that's interesting. You can't include main.cpp in Settings or in Patients.

No, but you might be including main.h, and maybe you have extern tetra_grip_api api; there, that's the sort of thing I was trying to understand. Which finally you have shown is actually in tetra_grip_api.h, which I guess you are including into each of them?

For the line there

extern tetra_grip_api api;

does the docs for tetra_grip_api say you are responsible for defining tetra_grip_api api; yourself like you have done in main.cpp, or does it say they (the library) are defining that global instance and you are supposed to use their instance?

jazzco2

@russjohn834 Yes, pass the pointer - and then your api can be a local variable in main. No need to define it outside as main lives as long as the application is running.

russjohn834

@jazzco2

Could you give me an example to show how do I pass a pointer to the constructor of the classes? for ex. if I need to use it in in Settings and Patients classes ?

jsulm

@russjohn834 said in same signal-slot connection in two windows:

Could you give me an example to show how do I pass a pointer to the constructor of the classes?

Well

tetra_grip_api api;
Settings settings(&api);

Of cource you have to change the constructor, but this is C++ basic stuff.

russjohn834

@JonB

it did not mention anything like that. My primary requirement is to use tetra_grip_api(which is a class containing all serial communication objects) instance in every form class. That's why I made it global, but now I realize it's not a good way of programming!

JonB

@russjohn834 said in same signal-slot connection in two windows:
Yes and no, it gets complicated. You may not need to pass it around that way.

It looks like the tetra_grip_api is something in-house to you, it does not exist on the web. You have shown that tetra_grip_api.h file contains the line:

extern tetra_grip_api api;  //----------> it leads me here

You should ask the author of that file whether he intends:

It is up to you to go tetra_grip_api api once in one of your own files, in order to define it, as you have done in your main.cpp; OR
The tetra_grip_api library already contains this definition for you, and you are supposed to use that one.

For now, humour me:

Go into your main.cpp. Locate the line which reads:

tetra_grip_api api; //-------------> api instance

Now comment out that line.

Try to rebuild & relink. What happens? Do you end up, after the linking, with an error message like: "Unresolved symbol: ''tetra_grip_api", or not?

If there is no error, see whether your program behaves correctly now.
If there is an error, unfortunately it's time we saw all your relevant code which should work but does not, because there is way too much incomplete information in what you have posted. I hesitate to say this, because I have a bad feeling that's going to be (at least) 3 .cpp files & 3 .h. files. Which is an awful lot for to paste and for us to look through :( If you could cut it down to a relevant, minimal subset which reproduces the bad behaviour you say you see, that would be really good....

russjohn834

@JonB Thanks a lot for your feedback.

Commenting out of tetra_grip_api api in the main.cpp did end up in multiple errors with "Unresolved external symbol class tetra_grip_api api".

From the suggestions from you guys, I feel like there is something wrong in making use of global variables. I should try also the other way of passing pointer to the class.

But I was trying to understand a reason program behaves this way.

As I mentioned earlier , If I call Patients behaves badly if I call it from Settings. But instead If I call both Patieints and Settings in the main (as shown below), both behave as expected. Do you immedatly think of any reason for this!?

#include <QApplication>

tetra_grip_api api;

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    api.openSerialPort();
    QObject::connect(api.serial, SIGNAL(readyRead()), &api, SLOT(readData()));
    QObject::connect(api.serial, SIGNAL(error(QSerialPort::SerialPortError)),&api, SLOT(ErrorHandler(QSerialPort::SerialPortError))); // error handling


    Settings  w(nullptr); //---->this behaves right
    Patients  v(nullptr); //---- >this behaves right
    v.show();
    w.show();

    return a.exec();
}

JonB

@russjohn834
No, because you show the case which works OK. We need to see exactly how Settings calls Patients, plus the signal connections, with whatever is relevant to that case, to judge where the problem is.