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How to send variables between classes in Qt


How to send variables between classes in Qt

By : TOLLYWOOD
Date : October 23 2020, 06:10 PM
it helps some times Use signals/slots mechanism to share values between two QObject.
For example:
code :
class Widget1: public QWidget
{
    Q_OBJECT
public:
    Widget1(): QWidget(),
        message(new QLineEdit())
    {
        QPushButton* button = new QPushButton("Send msg", this);
        connect(button, &QPushButton::clicked, this, [=]() { emit this->sendMsg(message->text());}); // When you click on the button, it will emit the signal sendMsg

        QVBoxLayout* layout = new QVBoxLayout(this);
        layout->addWidget(message);
        layout->addWidget(button);
    }
private:
    QLineEdit* message;
signals:
    void sendMsg(QString const& msg);
};
class Widget2: public QWidget
{
    Q_OBJECT
public:
    Widget2(): QWidget(),
        display(new QLabel("Nothing to display", this))
    {
        QVBoxLayout* layout = new QVBoxLayout(this);
        layout->addWidget(display);
    }
private:
    QLabel* display;
public slots:
    void receive(QString const& message)
    {
        display->setText(message); // When called, display the message in the label
    }
};
int main(int argc, char *argv[])
{
    QApplication app(argc, argv);

    QWidget* mainWidget = new QWidget();
    QHBoxLayout* layout = new QHBoxLayout(mainWidget);

    Widget1* w1 = new Widget1();
    Widget2* w2 = new Widget2();
    layout->addWidget(w1);
    layout->addWidget(w2);

    // When the signal sendMsg is emitted, call the slot receive
    QObject::connect(w1, &Widget1::sendMsg, w2, &Widget2::receive);

    mainWidget->show();
    return app.exec();
}


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Extending static classes in PHP - Avoiding sharing variables for multiple classes in extended class

Extending static classes in PHP - Avoiding sharing variables for multiple classes in extended class


By : Chris
Date : March 29 2020, 07:55 AM
I hope this helps . Since $className is static and within the parent class, when you set className within A or B, it changes the variable within the parent, and the same is done when the variable is read. Unless you override className in your extended classes, you'll be storing and retrieving information from the same memory location, originally defined in InstanceModule.
If you redefine className in A/B, you can access className using parent:: or self:: from InstanceModule or A/B respectively. Depending on what you are trying to do, Abstract classes may also play a significant role.
F# constructors and classes: Set up classes without extra mutable variables for each member property

F# constructors and classes: Set up classes without extra mutable variables for each member property


By : Ruby
Date : March 29 2020, 07:55 AM
Hope this helps So I have been looking at this page on the MSDN about constructors in F#. I am looking at the very first code sample , You can use this syntax
code :
type MyClass(property1 : int) =
    member val Property1 = property1
    member val Property2 = "" with get, set
Python: classes handling mutable variables in inherited classes which depend on parent class

Python: classes handling mutable variables in inherited classes which depend on parent class


By : Afzal Ali
Date : March 29 2020, 07:55 AM
wish help you to fix your issue You could use properties to accomplish this. You can then override the necessary properties in the child classes to achieve your desired result. For example:
code :
class CommonParent(object):

    @property
    def format_field(self):
        return u'parent_format'

    @property
    def mutable_field(self):
        return u'parent_replace'

    @property
    def result_string(self):
        return '{0} {1}'.format(self.mutable_field, self.format_field)


class Child1(CommonParent):
    @property
    def mutable_field(self):
        return u'child1_replace'


class Child2(CommonParent):
    @property
    def format_field(self):
        return u'child2_format'

    @property
    def mutable_field(self):
        return u'child2_replace'


class Result1(Child1):
    pass


class Result2(Child2):
    pass


if __name__ == '__main__':
    r1 = Result1()
    print(getattr(r1, 'result_string'))

    r2 = Result2()
    print(getattr(r2, 'result_string'))
child1_replace parent_format
child2_replace child2_format
Do classes not inherit static variables from the classes they extend?

Do classes not inherit static variables from the classes they extend?


By : Mahmoud Ziada
Date : March 29 2020, 07:55 AM
To fix the issue you can do That's correct. Static variables are not inherited by subclasses. This is documented here, which also suggests working around it by declaring an instance variable with the same name. Not sure how useful of a workaround that is, since you might as well change the static variable to an instance one instead of having both (unless you really need to call Animal.debug elsewhere), but it's AS3, it's there.
Send variables to other classes

Send variables to other classes


By : Eric James P Belleca
Date : March 29 2020, 07:55 AM
With these it helps Don't reinvent wheels, use the DateTime.TryParseExact method which is built specifically for this purpose. Forget about regexes and substrings when you are dealing with dates in the .NET framework:
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