Connecting two windows
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do you happen to have a function body inside mainwindow.cpp ?
somethinglike:
void MainWindow::patientID(QString string)That's not allowed for signals
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@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);
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@J-Hilk @russjohn834 I'm lost. The signal is declared in MainWindow, but connect is in StageOne.
@russjohn834 What is it now?! -
Still the same issue.
I changed the name of signal from
patientID
topatientIdChanged
.signal is Declared and emitted in
MainWindow
. Connection is inStageOne
(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
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@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*! }
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@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 fromQMainWindow
. Comes from doing Python all the time instead of C++. So I misled OP by saying put inthis
where he should havemainWindow
, my fault not his! -
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?
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#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 :) ) -
@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. -
@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
))? -
@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? -
@Pablo-J-Rogina Hi,
There are two forms.
MainWindow
andStageOne
(Both inherits QMainWindow).MainWindow
has a signalpatientIdChanged(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 aQLabel
, itssetText
should get signal (Qstring) value fromMainwWndow
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
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@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
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@Pablo-J-Rogina Thanks a lot that's exactly I was trying for.
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Thank you @JonB, @jsulm , @J-Hilk and @Pablo-J-Rogina for your feedback
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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 classStageOne
.
So we can assume that theStageOne
instance is built with specifying the parent as theMainWindow
, 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 signalpatientID
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); }
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@jhx76 said in Connecting two windows:
If i am right, the parent of the stageone object is the MainWindow from which the signal patientID is emitted.
it looks like there's no need to have signals at all.
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That's right :)
was just answering to the original question :
What I'm doing wrong here?
have a nice day
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@russjohn834 Just a tip: to avoid circular dependencies use forward declarations:
// a.h class B; // This is forward declaration for class B, no need to include b.h here class A { private: B *b; }; // b.h #include "a.h" ...
Forward declarations work only for pointers - in the above example it would not work if b would not be a pointer.
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@jsulm Thank you for your suggestion.
Just to further clarify myself the use of forward declaration:Two form classes
MainWindow
andStageOne
StageOne
needs to connect with a signal fromMainWindow
I did this in
StageOne
class MainWindow; // ---------> forward declaration for Mainwindow namespace Ui { class StageOne; } class StageOne : public QMainWindow { Q_OBJECT public: explicit StageOne(QString, QWidget *parent = nullptr); ~StageOne(); private: Ui::StageOne *ui; MainWindow *window; };
I'm trying to connect as follows in
StageOne
:connect(window,&MainWindow::patientIdChanged, ui->label, &QLabel::setText);
But this gives an error says:
stageone.cpp:12:21: error: incomplete type 'MainWindow' named in nested name specifier stageone.h:10:7: note: forward declaration of 'MainWindow'
in
mainwindow
, i did include#include "stageone.h"
what mistake I'm doing here?
Thank you