Signals and Slots between two classes

ktrsathish

I am facing problem on connecting the signals between two classes. I have create slots, signals and connected the same but signals are not received in slots. Could you please help me out to find the problem. Please find the code which I have implemented.

Form.H

#ifndef FORM_H
#define FORM_H

#include <QWidget>
#include "test.h"

namespace Ui {
class Form;
}

class Form : public QWidget
{
    Q_OBJECT

public:
    explicit Form(QWidget *parent = nullptr);
    ~Form();


signals:
    void valueChanged(int newValue);

private slots:
    void on_button_clicked();

    void off_button_clicked();

private:
    Ui::Form *ui;
    int value;
    Test obj;
};

#endif // FORM_H

Test.h

#ifndef TEST_H
#define TEST_H

#include <QtCore/qglobal.h>
#if QT_VERSION >= 0x050000
#include <QtWidgets/QWidget>
#else
#include <QtGui/QWidget>
#endif

class Test : public QWidget
{
    Q_OBJECT

    public:
        explicit Test(QWidget *parent = nullptr);
        void EnableImage(int value);

signals:
        void ValueChanged(int value);
};

#endif // TEST_H

widget.h

#ifndef WIDGET_H
#define WIDGET_H

#include <QWidget>
#include <QLabel>


namespace Ui {
class Widget;
}

class Widget : public QWidget
{
    Q_OBJECT



public:
    explicit Widget(QWidget *parent = nullptr);
    ~Widget();

    QLabel *Picture;

public slots:
    void setValue(int value);

public:
    Ui::Widget *ui;
};

#endif // WIDGET_H

form.cpp

#include "form.h"
#include "ui_form.h"

Form::Form(QWidget *parent) :
    QWidget(parent),
    ui(new Ui::Form)
{
    ui->setupUi(this);
    value = 0;
    Test obj;
}

Form::~Form()
{
    delete ui;
}

void Form::on_button_clicked()
{
    value = 1;
    obj.EnableImage(value);
}

void Form::off_button_clicked()
{
    value = 0;
    obj.EnableImage(value);
}

main.cpp

#include "widget.h"
#include "form.h"
#include "test.h"
#include <QApplication>
#include <QObject>


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

    Widget w;
    Form f;
    Test t;


    w.show();
    f.show();

    // help show windows apart
    f.move(w.geometry().left() + 50,w.geometry().top() + 50);

    QObject::connect(&t, SIGNAL(valueChanged(int)),
                         &w, SLOT(setValue(int)));


    return a.exec();
}

test.cpp

#include "test.h"

Test::Test(QWidget *parent) : QWidget(parent)
{

}

void Test::EnableImage(int value)
{
    emit ValueChanged(value);
}

widget.cpp
#include "widget.h"
#include "ui_widget.h"

Widget::Widget(QWidget *parent) :
    QWidget(parent),
    ui(new Ui::Widget)
{
    ui->setupUi(this);
    Picture = ui->image;
    Picture->hide();

}

void Widget::setValue(int value)
{
    if(value == 0)
    {
        Picture->hide();
    }
    else
    {
        Picture->show();
    }
}

Widget::~Widget()
{
    delete ui;
}

VRonin

Can you use the new connection syntax?
QObject::connect(&t, SIGNAL(valueChanged(int)),&w, SLOT(setValue(int))); should become QObject::connect(&t,&Test::valueChanged,&w,&Widget::setValue);

ktrsathish

@VRonin no change. signals are not recieved in slots.

Christian Ehrlicher

@ktrsathish said in Singals and Slots between two classes:

Form::Form(QWidget *parent) :
QWidget(parent),
ui(new Ui::Form)
{
ui->setupUi(this);
value = 0;
Test obj;
}

What should 'Test obj' do here?

void Form::on_button_clicked()
{
value = 1;
obj.EnableImage(value);
}

This is not the object you're doing your connect on.

ktrsathish

@Christian-Ehrlicher My actual implementaion shall follow the above architecture. so I have written the sample code to work first.

mrjj

@ktrsathish
Hi
Could you zip sample and upload via
~~https://www.justbeamit.com/~~ ( single use :( )
any other dropbox, Google drive, etc that can give a link
with no registration required to get it.

Code looks ok, but its easy to miss stuff due to all the scrolling.

ktrsathish

@mrjj https://drive.google.com/file/d/1d0Cc86uItT6F-ZzpbWtreATYICApRG1U/view?ts=5bd73a93
Please check the code and let me know the details.

mrjj

@ktrsathish
super !
but it asks permissions.
Can you remove that ?

ktrsathish

@mrjj https://drive.google.com/file/d/1d0Cc86uItT6F-ZzpbWtreATYICApRG1U/view?usp=sharing can you try now.

mrjj

@ktrsathish
Hi
In class Form, you have
private:
..
Test obj;

and you use that to emit

void Form::on_ABS_ON_clicked()
{
value = 1;
obj.EnableImage(value);
}

BUT
the one you hook up in main is another test instance
and its not used to emit the signal.

Test t;
 QObject::connect(&t, &Test::ValueChanged, &w, &Widget::setValue);

t is not the one u use to emit signal.

So that is why all looks fine but nothing happens.
The actual emitter object is not connected up.

So it was as mr. @Christian-Ehrlicher said / suggested

ktrsathish

@mrjj said in Signals and Slots between two classes:

Test t;
QObject::connect(&t, &Test::ValueChanged, &w, &Widget::setValue);

Thanks. It is solved.