In Qt with C++, what is the best way to access private members belonging to MainWindow, in a Dialog?
As a beginner in Qt with C++, I am having difficulty in accessing members of my MainWindow object from a Dialog object.
My dialog object is from a class called Month, and below is my code:
I have a comboBox in MainWindow where I want the user to select a month, and then store the string for that month in a private variable called monthSelected as follows:
void MainWindow::on_monthComboBox_activated(const QString &arg1)
{
monthSelected = arg1;
qDebug()<<"Month Selected is " << monthSelected << endl;
}
I get the correct output after selecting the month, but when I try to retrieve the value of monthSelected in my Month dialog class via a getter function, then I get an empty string as output.
Month::Month(QWidget *parent) :
QDialog(parent),
ui(new Ui::Month)
{
ui->setupUi(this);
MainWindow *mainWindow = new MainWindow();
qDebug()<<mainWindow->getMonthSelected();
}
As you can see, I created a pointer to MainWindow in order to access the getter function in my Month class, and I suspect this is where my error lies.
Is this the correct way to access members from the MainWindow class in a dialog, and if not, how would I go about doing it correctly?
c++ qt5
asked Nov 20 '18 at 13:23
CodeCanaryCodeCanary
11
|
show 9 more comments
As a beginner in Qt with C++, I am having difficulty in accessing members of my MainWindow object from a Dialog object.
My dialog object is from a class called Month, and below is my code:
I have a comboBox in MainWindow where I want the user to select a month, and then store the string for that month in a private variable called monthSelected as follows:
void MainWindow::on_monthComboBox_activated(const QString &arg1)
{
monthSelected = arg1;
qDebug()<<"Month Selected is " << monthSelected << endl;
}
I get the correct output after selecting the month, but when I try to retrieve the value of monthSelected in my Month dialog class via a getter function, then I get an empty string as output.
Month::Month(QWidget *parent) :
QDialog(parent),
ui(new Ui::Month)
{
ui->setupUi(this);
MainWindow *mainWindow = new MainWindow();
qDebug()<<mainWindow->getMonthSelected();
}
As you can see, I created a pointer to MainWindow in order to access the getter function in my Month class, and I suspect this is where my error lies.
Is this the correct way to access members from the MainWindow class in a dialog, and if not, how would I go about doing it correctly?
c++ qt5
asked Nov 20 '18 at 13:23
CodeCanaryCodeCanary
11
2
Why are you creating a new instance of MainWindow? That is not going to help at all this is a totally new object having nothing to do with the already existing MainWindow from your application.
– drescherjm
Nov 20 '18 at 13:37
1
Maybe theparentpointer is already the MainWindow? Who creates theMonthobject?
– drescherjm
Nov 20 '18 at 13:39
@drescherjm The Month object is created by the MainWindow when the user clicks on a button in the main window. Month *monthDialog = new Month(this);
– CodeCanary
Nov 20 '18 at 13:51
Then you already have a pointer to your MainWindow.
– drescherjm
Nov 20 '18 at 14:03
MainWindow* pMain = qobject_cast<MainWindow*>(parent);
– drescherjm
Nov 20 '18 at 14:04
|
show 9 more comments
As a beginner in Qt with C++, I am having difficulty in accessing members of my MainWindow object from a Dialog object.
My dialog object is from a class called Month, and below is my code:
I have a comboBox in MainWindow where I want the user to select a month, and then store the string for that month in a private variable called monthSelected as follows:
void MainWindow::on_monthComboBox_activated(const QString &arg1)
{
monthSelected = arg1;
qDebug()<<"Month Selected is " << monthSelected << endl;
}
I get the correct output after selecting the month, but when I try to retrieve the value of monthSelected in my Month dialog class via a getter function, then I get an empty string as output.
Month::Month(QWidget *parent) :
QDialog(parent),
ui(new Ui::Month)
{
ui->setupUi(this);
MainWindow *mainWindow = new MainWindow();
qDebug()<<mainWindow->getMonthSelected();
}
As you can see, I created a pointer to MainWindow in order to access the getter function in my Month class, and I suspect this is where my error lies.
Is this the correct way to access members from the MainWindow class in a dialog, and if not, how would I go about doing it correctly?
c++ qt5
asked Nov 20 '18 at 13:23
CodeCanaryCodeCanary
11
As a beginner in Qt with C++, I am having difficulty in accessing members of my MainWindow object from a Dialog object.
My dialog object is from a class called Month, and below is my code:
I have a comboBox in MainWindow where I want the user to select a month, and then store the string for that month in a private variable called monthSelected as follows:
void MainWindow::on_monthComboBox_activated(const QString &arg1)
{
monthSelected = arg1;
qDebug()<<"Month Selected is " << monthSelected << endl;
}
I get the correct output after selecting the month, but when I try to retrieve the value of monthSelected in my Month dialog class via a getter function, then I get an empty string as output.
Month::Month(QWidget *parent) :
QDialog(parent),
ui(new Ui::Month)
{
ui->setupUi(this);
MainWindow *mainWindow = new MainWindow();
qDebug()<<mainWindow->getMonthSelected();
}
As you can see, I created a pointer to MainWindow in order to access the getter function in my Month class, and I suspect this is where my error lies.
Is this the correct way to access members from the MainWindow class in a dialog, and if not, how would I go about doing it correctly?
c++ qt5
c++ qt5
asked Nov 20 '18 at 13:23
CodeCanaryCodeCanary
11
asked Nov 20 '18 at 13:23
CodeCanaryCodeCanary
11
asked Nov 20 '18 at 13:23
CodeCanaryCodeCanary
11
asked Nov 20 '18 at 13:23
CodeCanaryCodeCanary
11
asked Nov 20 '18 at 13:23
CodeCanaryCodeCanary
11
11
2
Why are you creating a new instance of MainWindow? That is not going to help at all this is a totally new object having nothing to do with the already existing MainWindow from your application.
– drescherjm
Nov 20 '18 at 13:37
1
Maybe theparentpointer is already the MainWindow? Who creates theMonthobject?
– drescherjm
Nov 20 '18 at 13:39
@drescherjm The Month object is created by the MainWindow when the user clicks on a button in the main window. Month *monthDialog = new Month(this);
– CodeCanary
Nov 20 '18 at 13:51
Then you already have a pointer to your MainWindow.
– drescherjm
Nov 20 '18 at 14:03
MainWindow* pMain = qobject_cast<MainWindow*>(parent);
– drescherjm
Nov 20 '18 at 14:04
|
show 9 more comments
2
Why are you creating a new instance of MainWindow? That is not going to help at all this is a totally new object having nothing to do with the already existing MainWindow from your application.
– drescherjm
Nov 20 '18 at 13:37
1
Maybe theparentpointer is already the MainWindow? Who creates theMonthobject?
– drescherjm
Nov 20 '18 at 13:39
@drescherjm The Month object is created by the MainWindow when the user clicks on a button in the main window. Month *monthDialog = new Month(this);
– CodeCanary
Nov 20 '18 at 13:51
Then you already have a pointer to your MainWindow.
– drescherjm
Nov 20 '18 at 14:03
MainWindow* pMain = qobject_cast<MainWindow*>(parent);
– drescherjm
Nov 20 '18 at 14:04
2
2
Why are you creating a new instance of MainWindow? That is not going to help at all this is a totally new object having nothing to do with the already existing MainWindow from your application.
– drescherjm
Nov 20 '18 at 13:37
Why are you creating a new instance of MainWindow? That is not going to help at all this is a totally new object having nothing to do with the already existing MainWindow from your application.
– drescherjm
Nov 20 '18 at 13:37
1
1
Maybe the
parent pointer is already the MainWindow? Who creates the Month object?– drescherjm
Nov 20 '18 at 13:39
Maybe the
parent pointer is already the MainWindow? Who creates the Month object?– drescherjm
Nov 20 '18 at 13:39
@drescherjm The Month object is created by the MainWindow when the user clicks on a button in the main window. Month *monthDialog = new Month(this);
– CodeCanary
Nov 20 '18 at 13:51
@drescherjm The Month object is created by the MainWindow when the user clicks on a button in the main window. Month *monthDialog = new Month(this);
– CodeCanary
Nov 20 '18 at 13:51
Then you already have a pointer to your MainWindow.
– drescherjm
Nov 20 '18 at 14:03
Then you already have a pointer to your MainWindow.
– drescherjm
Nov 20 '18 at 14:03
MainWindow* pMain = qobject_cast<MainWindow*>(parent);– drescherjm
Nov 20 '18 at 14:04
MainWindow* pMain = qobject_cast<MainWindow*>(parent);– drescherjm
Nov 20 '18 at 14:04
|
show 9 more comments
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2
Why are you creating a new instance of MainWindow? That is not going to help at all this is a totally new object having nothing to do with the already existing MainWindow from your application.
– drescherjm
Nov 20 '18 at 13:37
1
Maybe the
parentpointer is already the MainWindow? Who creates theMonthobject?– drescherjm
Nov 20 '18 at 13:39
@drescherjm The Month object is created by the MainWindow when the user clicks on a button in the main window. Month *monthDialog = new Month(this);
– CodeCanary
Nov 20 '18 at 13:51
Then you already have a pointer to your MainWindow.
– drescherjm
Nov 20 '18 at 14:03
MainWindow* pMain = qobject_cast<MainWindow*>(parent);– drescherjm
Nov 20 '18 at 14:04