Unable to send variable to another form

VJ01

Hi

I’m still new to QT and have just started using slots and signals. I’m trying to send a variable from one form to another, and then the other way back, however I wanted to attempt to do it one way first, however I’m getting an error which no matter what I try it won’t go away. I have two forms MainWindow and Settings my code is below

Mainwindow.h

signals:
    void SendData(int speed_check_mainform);

Settings.h

private slots:
    void getData(int speed_check_mainform);

Settings.cpp

void Settings::getData(int speed_check_mainform){
    qDebug() << speed_check_mainform;
}

MainWindow.cpp

connect(MainWindow,SIGNAL(SendData(int)),Settings,SLOT(getData(int)));

in the MainWindow.cpp is where i am getiing the error

expected primary-expression before ',' token

I’m not sure if it is something simple or not, I have looked at many examples online and I always get the same error from the connect, I have put it in the main() however still nothing. I of course know that I need to emit when using the signal but I just can’t seem to get passed this error. if anyone could help that would be great

Thank you

JonB

@VJ01 said in Unable to send variable to another form:

connect(MainWindow,SIGNAL(SendData(int)),Settings,SLOT(getData(int)));

At a guess, from your Settings.cpp extract void Settings::getData() it looks like Settings is a class name. For signal/slot you must connect instances (presumably MainWindow is one?), what is your Settings instance's variable?

Next, given you have declared the getData() slot as private in Settings.h obviously you are not going to be able to access it on a Settings instance anyway, only from within Settings class. If you want to connect() to it from the outside world/on an instance don't make it private, that is what private is there to prevent!

You should not be using SIGNAL/SLOT() macros for connect(), they are old-style from many years ago. You should be using new style, the error messages may be more helpful.

VJ01

@JonB hi thank you for the reply i tried to implement it a different way

MainWindow.cpp

void MainWindow::on_actionSettings_triggered()
{
 qDebug() << "Settings";
 Settings *dlg = new Settings();
     connect(this, SIGNAL(sendData(int)), dlg, SLOT(setData(int)));
     emit sendData(35);
 settings.show();
}

Settings.cpp

void Settings::setData(int data)
{
 printf("BLAH BLAH BLAH %d\n", data);
ui->lineEdit->setText(data);
}

my printf function does show that data is 35 however i cant seem to get the line Edit to work

Thank you

jsulm

@VJ01 said in Unable to send variable to another form:

however i cant seem to get the line Edit to work

Because setText expects a QString as you can clearly see in the documentation: https://doc.qt.io/qt-6/qlineedit.html#text-prop
So, convert the int to QString: https://doc.qt.io/qt-6/qstring.html#number-1

VJ01

@jsulm

sorry about that i pasted the wrong code

void Settings::setData(int data)
{
 printf("BLAH BLAH BLAH %d\n", data);
 ui->lineEdit->setText(QString::number(data));
}

this is the code im using but has the same effect and nothing happens
never mind i was just being really thick i should have done this in my MainWindow.cpp

 dlg->show();