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c++qtdynamicsignals-slotsslot

Is it possible to program function into Qt's SLOT() for QWidget or should use QSignalMapper?

In my Qt Application I am dynamically creating 'Questions' in QVBoxLayouts for a 'Questionnaire'. There are 3 types of Questions: Boolean, Text, & Radio.

When the user 'adds a question' to the questionnaire, they are presented with a QComboBox. When the index/text of this QComboBox is edited, I want to act upon the SIGNAL emitted.

I would like to have something like Java's (from an old Android Project):

button.setOnClickListener(new OnClickListener() {
        public void onClick(View v) {
            //Code to run...
        }
    });

Is it possible to have the same in Qt/C++ like:

connect(qvectorOfComboBoxes.at(qvectorOfComboBoxes.end()), SIGNAL(currentTextChanged(QString)),
            this, SLOT(
                    void comboBoxTextChanged(QString newComboxBoxText)
                    {
                        //This doesn't work
                    } )) ;

I understand from another post on here the ideal approach is a QSignalMapper, but was hoping to perform the task in a manner similar to above.

Usually, I find my answers either on here or from a related Google search (I am probably searching the wrong thing as I don't know the name for this), and so was hoping somebody here could give me a yay or nay. Thanks

Solution

  • In Qt5 and using a C++11-enabled compiler, you can use lambdas as slots, as explained here:

    connect(sender, SIGNAL(signal(QString)), [](QString newComboxBoxText) {
    // add your code here
});

    Otherwise, you can use sender() to query the QObject* which sent the signal, if this is enough information you need. To cast it to a QComboBox* please use qobject_cast<QComboBox*> and Q_ASSERT that it's not null. (You can't get a compile-time error that it was connected to some other type.)