signal and slots between two classes

[marlenet15]

I have two classes: signin and dialog. When I click a pushbutton on signin I want dialog to perform a slot. I have looked at forums and I believe I did the code correctly and I have no errors. However, when I try click the button nothing happens.

signin.h

#define SIGNIN_H

#include <QDialog>

namespace Ui {
class signin;
}

class signin : public QDialog
{
    Q_OBJECT

public:
    explicit signin(QWidget *parent = 0);
    ~signin();

signals:
    void clickedNextSignal();

private:
    Ui::signin *ui;
};

#endif // SIGNIN_H

signin.cpp

#include "ui_signin.h"

signin::signin(QWidget *parent) :
    QDialog(parent),
    ui(new Ui::signin)
{
    ui->setupUi(this);

    connect(ui->nextButtonSignin, SIGNAL(clicked()),this,SIGNAL(clickedNextSignal()));
}

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

dialog.h

#define DIALOG_H

#include <QDialog>
#include "signin.h"
#include "ui_signin.h"

namespace Ui {
class Dialog;
}

class Dialog : public QDialog
{
  Q_OBJECT

public:
  explicit Dialog(QWidget *parent = 0);
  ~Dialog();

public slots:
  void openBox();

private:
  Ui::Dialog *ui;

protected:
  signin *_signin;

};

#endif // DIALOG_H

dialog.cpp

#include "ui_dialog.h"
#include <QMessageBox>

Dialog::Dialog(QWidget *parent) :
    QDialog(parent),
    ui(new Ui::Dialog)
{
    ui->setupUi(this);

    _signin = new signin(this);

    connect(_signin , SIGNAL(clickedNextSignal()),this,SLOT(openBox()));
}

void Dialog::openBox()
{
    QMessageBox::information(this,tr("title"),tr("hi"));
}

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

[mrjj]

Hi
One thing I saw
connect(ui->nextButtonSignin, SIGNAL(clicked()),this,SIGNAL(clickedNextSignal()));
should have been SLOT in last.

If possible, use the new syntax as it has more type checking

connect( ui->nextButtonSignin, &QPushButton::clicked, this, &Dialog::clickedNextSignal);
(If nextButtonSignin is QPushbutton)

Hmm, there is something odd going on:
signin has signal clickedNextSignal but you never call
emit clickedNextSignal()
so in Dialog::Dialog
when you say
connect(_signin , SIGNAL(clickedNextSignal()),this,SLOT(openBox()));
Its correct but since signin do not emit (send) signal then nothing will happen.

So if you add a slot to sign in, lets cal lit DoNext (bad name:)
and hook it up to the button
connect(ui->nextButtonSignin, SIGNAL(clicked()),this,SLOT(DoNext()));
and in
void DoNext() {
emit clickedNextSignal();
}
Then the connect in Dialog should be more fun,
So in short.
NextButton clicked goes to signin slot that emit clickedNextSignal signal , that is hooked up to Dialog openBox().

Hope it helps.

[marlenet15]

This post is deleted!

[mrjj]

@marlenet15
Ok, as far as I know you cannot connect signal to signal but you can
connect multiple signals to one slot.

Did you place break point to see if the DoNext is called and
also check in application output that none of the connets return fail.
maybe even
qDebug() << " result:" << connect(ui->nextButtonSignin, SIGNAL(clicked()),this,SLOT(DoNext())); for both connect to see
if they are successful.

[marlenet15]

@mrjj I read from somewhere that you can have connect with two signals. I did try your recommendation but nothing happens.

[mrjj]

also how does you main.cpp look like ?

You show the Dialog instead of mainwindow?

[marlenet15]

@mrjj

#include "dialog.h"
#include <QApplication>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    Dialog *w = new Dialog();
    w->showNormal();

    return a.exec();
}``` 

and yes I used Dialog instead of mainwindow

[mrjj]

@marlenet15 said:
Hi I think the dialog in dialog mess up something.
Didnt work for me if I new the sign dialog in Start dialog constructor.
But it does work if I hooked it up outside.
Have a look at this example
https://www.dropbox.com/s/bvpps7qd8oovtjf/gonext.zip?dl=0
Its the same idea but created slightly different.

[marlenet15]

@mrjj I followed your example but it is still not working.

[mrjj]

@marlenet15
??
so the getnext example which runs here do no work when you compile it?

[marlenet15]

@mrjj ok it works. I redid my code using only QWidgets and it works. I think I know the problem and I forgot to mention it. I made QDialog a stacked widget and promoted the file signin.

[JKSH]

@mrjj said:

Ok, as far as I know you cannot connect signal to signal

You can. See the documentation:

You can connect as many signals as you want to a single slot, and a signal can be connected to as many slots as you need. It is even possible to connect a signal directly to another signal. (This will emit the second signal immediately whenever the first is emitted.)

[mrjj]

@JKSH
Aha, that is news for me. so that is like a chain signal or almost like an alias.

@marlenet15
Super. not sure what the real reason was but as long as it works :)

[marlenet15]

@mrjj Before creating the stackedwidget it worked. After adding it, it doesn't work anymore.

[mrjj]

@marlenet15
Ok. do you promote a qDialog to a stackwidget ?
Not sure I fully understand.
At least I have never tried that.

[marlenet15]

@mrjj on the .ui file of the class dialog, I created a stackedwidget and promoted the file signin.h

[mrjj]

@marlenet15
so the signin dialog was sort of inline to Dialog ?

[marlenet15]

@mrjj can you exaplain what you mean by that? Sorry

[mrjj]

@marlenet15
Hi np.
Im not 100% sure what you did.
If you promote a widget to a dialog.
the dialog will be sort of inside the parent/widget that contains the
promoted widget.
So I wondered if you promoted a stacked widget to the signin dialog ?

[marlenet15]

@mrjj I created a stackedwidget in dialog.ui, in there I promoted signin.h into the stackedwidget.