Handling signal-slot

[sudhansu]

Hi All
I've a doubt on signal and slot mechanisim. E.g

class  A
{
           signals:
             void sig();
}
 
class B
{
     public:
      A objOfA;
}
 
 
class C
{
    B objOfB;
   C();
public slots:
  void slot();
}
 
C::C()
{
      connect(&objOfB.objOfA,SIGNAL(sig(),this SLOT(slot()); /// Can we handle like this???
}

class  A
{
           signals:
             void sig();
}

class B
{
     public:
      A objOfA;
}


class C
{
    B objOfB;
   C();
public slots:
  void slot();
}

C::C()
{
      connect(&objOfB.objOfA,SIGNAL(sig(),this SLOT(slot()); /// Can we handle like this???
}

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My doubt is can we handle the signal as above?

Thank you all.

[faldzip]

If you add missing parentheses to connect() statement and make your classes derived from QObject then this should work.

[sudhansu]

If you add missing parentheses to connect() statement and make your classes derived from QObject then this should work.

Hi,
By mistake i forgot to add paranthesis,. And my class is derived from QDialog,(and QDialog is derived fromQWidget->QObject), SO i think no need to directly derived it from QObject.
But still its not working?.

[franz]

Eh, what exactly isn't working?

[faldzip]

Can you explain what does it mean "not working"? Any warnings on console output? Can you show exact code? Or prepare minimal compilable example reproducing your problem (but do not give us your whole project, but write something like in first post but make compilable).

[sudhansu]

Can you explain what does it mean "not working"? Any warnings on console output? Can you show exact code? Or prepare minimal compilable example reproducing your problem (but do not give us your whole project, but write something like in first post but make compilable).

Below i'm posting the code

class CMainWindow : public QDialog, public Ui::Dialog
{
    Q_OBJECT
 
    MessageBox MessageBoxObj;
 
   public:
    CMainWindow();
 
 
   public slots:
   void HandelMessage(QString i_strMessage);
}
CMainWindow()::CMainWindow()
{
    connect(&(MessageBoxObj.networklayerObj),SIGNAL(MessageFromNetworkLayer(QSTring )),this,SLOT( HandelMessage(QString)));
}
 
class MessageBox : public QDialog, public Ui::MessageDialog
{
    Q_OBJECT
 
    public:
      Network networklayerObj;
}
 
class Network:public QObject
{
O_OBJECT
 
    signals:
    void MessageFromNetworkLayer(QSTring message);
}

class CMainWindow : public QDialog, public Ui::Dialog
{
    Q_OBJECT
    
    MessageBox MessageBoxObj;
   
   public:
    CMainWindow();


   public slots:
   void HandelMessage(QString i_strMessage);
}
CMainWindow()::CMainWindow()
{
    connect(&(MessageBoxObj.networklayerObj),SIGNAL(MessageFromNetworkLayer(QSTring )),this,SLOT( HandelMessage(QString)));
}

class MessageBox : public QDialog, public Ui::MessageDialog
{
    Q_OBJECT

    public:
      Network networklayerObj;
}
 
class Network:public QObject
{
O_OBJECT

    signals:
    void MessageFromNetworkLayer(QSTring message);
}

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Please ignore the spelling mistakes.

[faldzip]

Ok, so:
1. What is not working?
2. Can check if there is any warning on console output?

[sudhansu]

Ok, so:
1. What is not working?
2. Can check if there is any warning on console output?

While debugging, i found that signal is emiting with some data, but its not connected to slot.
Debug statment inside slot also not priting, if i run the application.

[faldzip]

Don't you have any warning on console output like:
WARNING: no matching slot ...
?

For me this is working:

#include <QtCore>
 
class A : public QObject
{
	Q_OBJECT
public:
	A() : QObject(0), eventno(0) {
		startTimer(2000);
	}
protected:
	void timerEvent(QTimerEvent *) {
		if (++eventno == 2)
			QCoreApplication::quit();
		else
			emit message("Some useful message!");
	}
private:
	int eventno;
signals:
	void message(const QString &str);
};
 
class B : public QObject
{
	Q_OBJECT
public:
	B() : QObject(0) { }
	A aObj;
};
 
class C : public QObject
{
	Q_OBJECT
public:
	C() : QObject(0) {
		connect(&(bObj.aObj), SIGNAL(message(QString)), this, SLOT(showMessage(QString)));
	}
public slots:
	void showMessage(const QString &str) {
		qDebug(str.toLocal8Bit().constData());
	}
private:
	B bObj;
};
 
int main(int argc, char **argv)
{
	QCoreApplication a(argc, argv);
	C cObj;
	return a.exec();
}
 
#include "main.moc"

#include <QtCore>

class A : public QObject
{
	Q_OBJECT
public:
	A() : QObject(0), eventno(0) {
		startTimer(2000);
	}
protected:
	void timerEvent(QTimerEvent *) {
		if (++eventno == 2)
			QCoreApplication::quit();
		else
			emit message("Some useful message!");
	}
private:
	int eventno;
signals:
	void message(const QString &str);
};

class B : public QObject
{
	Q_OBJECT
public:
	B() : QObject(0) { }
	A aObj;
};

class C : public QObject
{
	Q_OBJECT
public:
	C() : QObject(0) {
		connect(&(bObj.aObj), SIGNAL(message(QString)), this, SLOT(showMessage(QString)));
	}
public slots:
	void showMessage(const QString &str) {
		qDebug(str.toLocal8Bit().constData());
	}
private:
	B bObj;
};

int main(int argc, char **argv)
{
	QCoreApplication a(argc, argv);
	C cObj;
	return a.exec();
}

#include "main.moc"

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[lyuts]

I 'm not sure whether you typed your code or just copied-pasted, but your class definition has to end with "};".