QObject connection, why do I have to add sender twice?

kocka

This function find QPushButton by their name.

QPushButton *MainWindow::findByObjName(QWidget *widget, QString objName) {
    return widget->findChild<QPushButton *>(objName);
}

findByObjName(widget,"pushButton_xx")->connect(findByObjName(widget,"pushButton_xx"), &QPushButton::clicked, this, [=]{MainWindow::function(widget);});

Why do I have to add findByObjName(widget,"pushButton_xx") twice?
Is there a case where I need to use this method?

jeremy_k

@kocka said in QObject connection, why do I have to add sender twice?:

@fcarney
@raven-worx

Okey, I but why there is a opportunity, to call connect as a reference of individual member of QPushButton class?

C++ allows accessing a static class member via the scope operator, eg Class::member, or via an object that is an instance of the class, such as objectPtr->member or objectRef.member.
https://en.cppreference.com/w/cpp/language/static

raven-worx

@kocka
you dont have to.

You can remove it when you are inside a QObject, or add QObject:: namespace to it

fcarney

The connect just needs to be run on QObject. I believe connect is static.

QObject::connect(findByObjName(widget,"pushButton_xx"), &QPushButton::clicked, this, [=]{MainWindow::function(widget);});

// Also, you can store your object for reuse:
auto foundObject = findByObjName(widget,"pushButton_xx");
QObject::connect(foundObject, &QPushButton::clicked, this, [=]{MainWindow::function(widget);});

This works because QPushButton base class is QObject.

kocka

@fcarney
@raven-worx

Okey, I but why there is a opportunity, to call connect as a reference of individual member of QPushButton class?

raven-worx

@kocka
because the connect method is public in the QObject class and QWidget inherits QObject

jeremy_k

@kocka said in QObject connection, why do I have to add sender twice?:

@fcarney
@raven-worx

Okey, I but why there is a opportunity, to call connect as a reference of individual member of QPushButton class?

C++ allows accessing a static class member via the scope operator, eg Class::member, or via an object that is an instance of the class, such as objectPtr->member or objectRef.member.
https://en.cppreference.com/w/cpp/language/static