Connecting two windows

[jsulm]

@russjohn834 Please show the exact declaration of patientID...

[russjohn834]

@jsulm Hi,

I declared patientID as:

QT_BEGIN_NAMESPACE
namespace Ui { class MainWindow; }
QT_END_NAMESPACE

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    MainWindow(QWidget *parent = nullptr);
    ~MainWindow();
    StageTwoNew *stagetwonew;
    StageOne *stageone;

signals:

    void patientID(QString);  ----------------> signal declaration


public slots:
    void on_pushButton_New_clicked();

    void on_pushButton_Open_clicked();

    void parseDataEntry(const QString dataPath);

private:
    Ui::MainWindow *ui;

};
#endif // MAINWINDOW_H

[jsulm]

@russjohn834 Looks good. Try a complete rebuild: delete build folder, run qmake and then build.

[russjohn834]

@jsulm

I'm getting still the same error:

stageone.cpp:11:5: error: no matching member function for call to 'connect'
qobject.h:228:43: note: candidate function [with Func1 = void (MainWindow::*)(QString), Func2 = void (QLabel::*)(const QString &)] not viable: no known conversion from 'StageOne *' to 'const typename QtPrivate::FunctionPointer<void (MainWindow::*)(QString)>::Object *' (aka 'const MainWindow *') for 1st argument
qobject.h:208:36: note: candidate function not viable: no known conversion from 'void (MainWindow::*)(QString)' to 'const char *' for 2nd argument
qobject.h:211:36: note: candidate function not viable: no known conversion from 'void (MainWindow::*)(QString)' to 'const QMetaMethod' for 2nd argument
qobject.h:463:41: note: candidate function not viable: no known conversion from 'void (MainWindow::*)(QString)' to 'const char *' for 2nd argument
qobject.h:269:13: note: candidate template ignored: requirement '!QtPrivate::FunctionPointer<void (QLabel::*)(const QString &)>::IsPointerToMemberFunction' was not satisfied [with Func1 = void (MainWindow::*)(QString), Func2 = void (QLabel::*)(const QString &)]
qobject.h:308:13: note: candidate template ignored: requirement 'QtPrivate::FunctionPointer<void (QLabel::*)(const QString &)>::ArgumentCount == -1' was not satisfied [with Func1 = void (MainWindow::*)(QString), Func2 = void (QLabel::*)(const QString &)]
qobject.h:260:13: note: candidate function template not viable: requires 3 arguments, but 4 were provided
qobject.h:300:13: note: candidate function template not viable: requires 3 arguments, but 4 were provided

This is how I call the connect:

#include "stageone.h"
#include "ui_stageone.h"
#include "mainwindow.h"

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

    connect(this, &MainWindow::patientID, ui->label, &QLabel::setText);  //

}

Any idea?

[J.Hilk]

@russjohn834

do you happen to have a function body inside mainwindow.cpp ?

somethinglike:
void MainWindow::patientID(QString string)

That's not allowed for signals

[J.Hilk]

@russjohn834 said in Connecting two windows:

connect(this, &MainWindow::patientID, ui->label, &QLabel::setText);

Oh its much simpler

You class is not called MainWindow, but StageOne

connect(this, &StageOne::patientID, ui->label, &QLabel::setText); 

[jsulm]

@J-Hilk @russjohn834 I'm lost. The signal is declared in MainWindow, but connect is in StageOne.
@russjohn834 What is it now?!

[russjohn834]

@jsulm @J-Hilk ,

Still the same issue.

I changed the name of signal from patientID to patientIdChanged.

signal is Declared and emitted in MainWindow. Connection is in StageOne (with a QLabel).

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

    connect(this, &MainWindow::patientIdChanged, ui->label, &QLabel::setText);  //
}

the error says:

stageone.cpp:11:5: error: no matching member function for call to 'connect'
qobject.h:228:43: note: candidate function [with Func1 = void (MainWindow::*)(QString), Func2 = void (QLabel::*)(const QString &)] not viable: no known conversion from 'StageOne *' to 'const typename QtPrivate::FunctionPointer<void (MainWindow::*)(QString)>::Object *' (aka 'const MainWindow *') for 1st argument
qobject.h:208:36: note: candidate function not viable: no known conversion from 'void (MainWindow::*)(QString)' to 'const char *' for 2nd argument
qobject.h:211:36: note: candidate function not viable: no known conversion from 'void (MainWindow::*)(QString)' to 'const QMetaMethod' for 2nd argument
qobject.h:463:41: note: candidate function not viable: no known conversion from 'void (MainWindow::*)(QString)' to 'const char *' for 2nd argument
qobject.h:269:13: note: candidate template ignored: requirement '!QtPrivate::FunctionPointer<void (QLabel::*)(const QString &)>::IsPointerToMemberFunction' was not satisfied [with Func1 = void (MainWindow::*)(QString), Func2 = void (QLabel::*)(const QString &)]
qobject.h:308:13: note: candidate template ignored: requirement 'QtPrivate::FunctionPointer<void (QLabel::*)(const QString &)>::ArgumentCount == -1' was not satisfied [with Func1 = void (MainWindow::*)(QString), Func2 = void (QLabel::*)(const QString &)]
qobject.h:260:13: note: candidate function template not viable: requires 3 arguments, but 4 were provided
qobject.h:300:13: note: candidate function template not viable: requires 3 arguments, but 4 were provided

[jsulm]

@russjohn834 Come on it is not about patientID!
In the connect bellow this is NOT MainWindow, but StageOne!
It simply can't work this way!

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

    connect(this, &MainWindow::patientIdChanged, ui->label, &QLabel::setText);  // this != MaiNWindow*!
}

If you want to connect in StageOne then you need an instance of MainWindow:

StageOne::StageOne(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::StageOne)
{
    ui->setupUi(this);
    MainWindow *mainWindow = new MainWindow(...);
    connect(mainWindow, &MainWindow::patientIdChanged, ui->label, &QLabel::setText);  // this != MaiNWindow*!
}

[JonB]

@jsulm
This is partly due to my bad... :(

No declaration of StageOne was shown. I quickly read:

StageOne::StageOne(QWidget *parent) :
    QMainWindow(parent)

I read it too quickly, and thought StageOne was derived from QMainWindow. Comes from doing Python all the time instead of C++. So I misled OP by saying put in this where he should have mainWindow, my fault not his!

[russjohn834]

I'm a bit lost!

I now get a different error

mainwindow.h:25: error: C2143: syntax error: missing ';' before '*'
mainwindow.h:25: error: C4430: missing type specifier - int assumed. Note: C++ does not support default-int
mainwindow.h:25: error: C2238: unexpected token(s) preceding ';'

this is my mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QDebug>
#include <QFile>
#include <QDirIterator>
#include <QXmlStreamReader>
#include <QMessageBox>
#include "stagetwonew.h"
#include "stageone.h"

QT_BEGIN_NAMESPACE
namespace Ui { class MainWindow; }
QT_END_NAMESPACE

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    MainWindow(QWidget *parent = nullptr);
    ~MainWindow();
    StageTwoNew *stagetwonew;
    StageOne *stageone;  ------------------>error points here

signals:

    void patientIdChanged(QString);


private slots:

    void on_pushButton_New_clicked();

    void on_pushButton_Open_clicked();

    void parseDataEntry(const QString dataPath);

private:
    Ui::MainWindow *ui;

};
#endif // MAINWINDOW_H

I tried complete rebuild, no luck

Any ideas where I'm wrong?

[JonB]

@russjohn834

#include "stagetwonew.h"
#include "stageone.h"
...
    StageTwoNew *stagetwonew;
    StageOne *stageone;  ------------------>error points here

Prove to us/yourself that those two header files declare StageTwoNew & StageOne as classes? (Having said that, I'd more have expected "undeclared", but at least check what I've said, even if I did mis-lead you earlier :) )

[jsulm]

@JonB said in Connecting two windows:

I read it too quickly, and thought StageOne was derived from QMainWindow

It apparently is derived from QMainWindow, but this does not have anything to do with your MainWindow.
Does StageOne include mainwindow.h? If so you have circular dependency.

[russjohn834]

@jsulm , @JonB

@jsulm said in Connecting two windows:

Does StageOne include mainwindow.h? If so you have circular dependency.

Yes. StageOne inlcude mainwindow.h. Any suggestion, How do I go about with circular dependency in this scenario?

Or is there a better way to do this (connect between two forms (QMainWindow))?

[Pablo J. Rogina]

@russjohn834 could you please state your requirement again?
How are the window(s) suppose to work together?
What data you want from what window updating what widget in what other window?

[russjohn834]

@Pablo-J-Rogina Hi,

There are two forms.
MainWindow and StageOne (Both inherits QMainWindow).

MainWindow has a signal patientIdChanged(QString), which is emitted upon clicking a button, I did this:

void MainWindow::on_pushButton_Open_clicked()
{

    QModelIndexList selection=ui->tableWidget->selectionModel()->selectedRows(0);

    this->hide();
    stageone = new StageOne(this);
    stageone->show();
    
  emit patientIdChanged(selection[0].data().toString());
    
    
}

And in StageOne I have a QLabel, its setText should get signal (Qstring) value from MainwWndow and show. That's the requirement.

I tried to do this in StageOne:

 MainWindow *mainWindow= new MainWindow(this);
connect(mainWindow, &MainWindow::patientIdChanged, ui->label, &QLabel::setText);

But this is not working

[Pablo J. Rogina]

@russjohn834 said in Connecting two windows:

Ok, it looks like you're overcomplicating things here.

So you want a string (some selection in MainWindow widget) passed to StageOne window, right?
What about having the StageOne constructor receiving such string? Pseudo-code:

void MainWindow::on_pushButton_Open_clicked()
{
     QModelIndexList selection=ui->tableWidget->selectionModel()->selectedRows(0);
 
     this->hide();
     stageone = new StageOne(selection[0].data().toString(), this);
     stageone->show();
...

and obviusly StageOne class need a change in constructor:

StageOne::StageOne(Qstring someString, QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::StageOne)
{
...

I don't see the need to deal with signals here

[russjohn834]

@Pablo-J-Rogina Thanks a lot that's exactly I was trying for.

[russjohn834]

Thank you @JonB, @jsulm , @J-Hilk and @Pablo-J-Rogina for your feedback

[jhx76]

Hi everybody.

Let's have a look to the code @russjohn834 gave us :

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    MainWindow(QWidget *parent = nullptr);
    ~MainWindow();
    StageTwoNew *stagetwonew;
    StageOne *stageone; 

signals:

    void patientID(QString);  ----------------> signal declaration


public slots:
    void on_pushButton_New_clicked();

    void on_pushButton_Open_clicked();

    void parseDataEntry(const QString dataPath);

private:
    Ui::MainWindow *ui;

};
#endif // MAINWINDOW_H

Here we can see that the MainWindow owns an object of the class StageOne.
So we can assume that the StageOne instance is built with specifying the parent as the MainWindow, certainly with code that looks like this :

MainWindow::MainWindow() : QMainWindow() 
    : stageone(new StageOne(this))
{
}

If i am right, the parent of the stageone object is the MainWindow from which the signal patientID is emitted.

You can then write things like this :

StageOne::StageOne(QWidget *parent) :
    QMainWindow(parent), // HERE the pointed parent is the MainWindow object
    ui(new Ui::StageOne)
{
    ui->setupUi(this);
    
    // We connect the MainWindow::patientID signal emitted from the parent object
    // to the QLabel::setText slot
    connect(parent, &MainWindow::patientID, ui->label, &QLabel::setText);  
}