same signal-slot connection in two windows

russjohn834

I'm connecting with the same signal in the previous window , so do I need to disconnect that and connection to use the same signal in with a new slot?

Basically in Settings window this works:

 connect(&api, &tetra_grip_api::tetraGripEvent,this, &Settings::eventHandler); //--> slot is eventHandler

But in Patients this is not working:

   connect(&api, &tetra_grip_api::tetraGripEvent,this, &Patients::eventHandlerTwo);//--->Slot is eventHandlerTwo

JonB

@russjohn834
So I now take it you mean you find the slot does not get entered, not the the connect fails?

No, you do not have to disconnect, a signal may have any number of slots attached. Though if a previously-attached slot does not return, or misbehaves like if the slot instance is no longer around, it is possible the second slot might not get called.

So if debugging what is going you might be advised to temporarily not connect the Settings slot, just the Patients slot and concentrate on sorting that out. It is not possible to say from what you have posted why one slot works and the other does not.

russjohn834

@JonB Thank you. I tried to connect only the Patients slot but cant see where I'm wrong..

Patients window is opened from Settings as given below:

void Settings::on_pushButton_patients_clicked()
{

    hide();
    stagetwo = new Patients(this);
    stagetwo -> show();
}

Where stagetwo is public

public:
     Settings(QString,QWidget *parent = nullptr);
    ~Settings();
     Patients *stagetwo;

Anything wrong I'm doing here!?

russjohn834

Hi all,

I just noticed this thing if I call both my Settings and Patients from my main the connection is successful (see below)

#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);
    w.show();

    Patients v(nullptr); //---------> this makes connection successfull
    v.show();

    return a.exec();
}

but instead, if I call Patients from Settings even though the connection is successful im not getting the expected output.

My signal source api is a global variable which is initialized in the main as shown above.
So constructing both classes in the main makes connection ok and I'm gettting expected output. But if I call one window from other makes connection true but my slot is not being called at all.

What is the reason for this?

JonB

@russjohn834
If you're asking me to guess, show how you gain access to tetra_grip_api api; from Settings/Patients? In these cases where do you do the connect()s from? And, how do you know your connect()s are successful?

SGaist

Hi,

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

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

Since serial is internal to api why don't you connect it in the constructor of your tetra_grip_api class ?

russjohn834

@JonB

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.