QT - connecting QPushButtons with QCheckBoxes

Question

I am new to QT. I started creating a TODO app and I want to somehow connect my PushButtons that are placed in vector with CheckBoxes that are also placed in a different vector.

std::vector <QPushButton*> buttons;
std::vector <QCheckBox*> checks;

I thought that the best way to do that will be to make a for loop connecting every element of mentioned vectors

Something like:

for(int i=0; i<buttons.size(); ++i){
    connect(buttons[i], SIGNAL(???), checks[i], SLOT(???));
}

But idea is the only thing that I have. I tried putting different things into SIGNAL() and SLOT() but none of them worked. By "none of them worked" I mean the fact that when button is clicked nothing happens. Program is normally compiled without any error.

Answer 1

What about just clicked(bool) for SIGNAL and toggle() for SLOT ?

Something like that:

connect(pushButton, SIGNAL(clicked(bool)), checkBox, SLOT(toggle()));

Answer 2

Works for me - and you can store the widgets directly in a std::list : that avoids the need to mess with manual memory management. Let the libraries do it for you.

#include <QtWidgets>
#include <list>
int main(int argc, char **argv) {
   QApplication app{argc, argv};
   QWidget win;
   QGridLayout layout{&win};
   std::list<QPushButton> buttons;
   std::list<QCheckBox> checkboxes;
   QPushButton addButton{"Add"};
   layout.addWidget(&addButton, 0, 0, 2, 1);
   auto const clicked = &QAbstractButton::clicked;
   auto const toggle = &QAbstractButton::toggle;
   auto const add = [&,clicked,toggle]{
      int const col = layout.columnCount();
      auto const text = QString::number(col);
      auto *button = &(buttons.emplace_back(text), buttons.back()); //C++11, not 14
      auto *checkbox = &(checkboxes.emplace_back(text), checkboxes.back());
      layout.addWidget(button, 0, col);
      layout.addWidget(checkbox, 1, col);
      QObject::connect(button, clicked, checkbox, toggle);
   };
   add();
   QObject::connect(&addButton, clicked, add);
   win.show();
   return app.exec();
}

Answer 3

With Qt-5 you can now use lambda functions as slots (see connect version 5 )

You can also do away with the need for the SIGNAL macro, and instead use member function pointers.

QObject::connect(buttons[i], &QPushButton::clicked, [=]
    {
        // toggle the check state
        checks[i]->setChecked(!checks[i]->isChecked());
    });

The first two parameters are a pointer to an object, and a member function pointer

• buttons[i] is of type QPushButton*
• &QPushButton::clicked is a member function pointer of the signal you want to connect to

The second parameter is a C++11 lambda, which captures checked and i by value, and then sets the QCheckBox checked state to the inverse of its previous value