How to connect QObbject (QPushButton) to a method from other class? - c++

Question

I'm currently working on a project that need the connection between a QPushButton of a Qwidget class (window) and a void method from a "classical" class.
I've tried to connect them with all the solution that I've read but none works correctly.
Either the compiler returns me
QObject::connect: No such slot QWidget::Class::metoh()
or it won't compile at all without errors.
Here's the simpliest code that I've tried. I read the Qt documentation but it didn't help me. I've also tried to include the Q_OBJECT Macro but it lead to errors. I've also read that with Qt5 it's no more mandatory to define slots. Have I understood correctly ?
How can I connect the Some_Class method to the QPushButton ?
// Classical class header //
#ifndef DEF_CLASS
#define DEF_CLASS
#include <iostream>
#include <cstdlib>
#include <string>
class Some_class
{
protected: // permet l'acces pour les methodes style soin
Some attributes;
public:
Some_Class(int id);
//Personnage(int id, int vieAtStart, int degatsArmeAtStart);
void method();
// obligation de passer par des references pour avoir une modification effective
~Some_Class();
};
#endif
// Classical class cpp //
#include "Some_Class.h"
#include <QObject>
#include <iostream>
#include <cstdlib>
#include <string>
#include <vector>
using namespace std;
Some_Class::Some_Class(int id)
{
Id = id;
some attributes;
};
void Some_Class::method()
{
modification of attributes;
};
// Window class header //
#ifndef DEF_WINDOW
#define DEF_WINDOW
#include <QApplication>
#include <QWidget>
#include <QLabel>
#include <QPushButton>
#include <QHBoxLayout>
#include <QVBoxLayout>
#include <QIcon>
#include <QGraphicsScene>
#include <QGraphicsView>
#include <QImage>
#include <QPixmap>
#include <QLabel>
#include <QGraphicsPixmapItem>
#include "Some_Class.h"
class Window : public QWidget // On hérite de QWidget (IMPORTANT)
{
public:
Window(Some_Class test);
// public slots:
// void go_right();
private:
QPushButton *m_button;
};
#endif
// Window class cpp //
#include "Window.h"
#include <string>
#include <QObject>
Window::Window(Some_Class test) : QWidget()
{
setFixedSize(874, 968);
m_button = new QPushButton("test", this);
QObject::connect(m_button, SIGNAL(clicked()), this, SLOT(Some_Class::method()));
//QObject::connect(m_bouton_droite, SIGNAL(clicked()), qApp, Personnage::go_right());
//QObject::connect(m_bouton_droite, &QPushButton::clicked,qApp, Personnage::go_right());
}
#include <QApplication>
#include <QHBoxLayout>
#include <QVBoxLayout>
#include <QLabel>
#include <QIcon>
#include "Window.h"
#include "Some_Class.h"
#include <QObject>
// main.cpp //
int main(int argc, char *argv[])
{
QApplication app(argc, argv);
Window win(Heros);
win.show();
return app.exec();
}

Answer 1

First, you will need an object of Some_Class with an appropriate scope. Currently you only have test in your constructor which is a value parameter and thus gets destroyed when the constructor returns. One option would be to pass in test as a pointer if the object you are passing in has the correct lifetime.
Window::Window(Some_Class *test)
If that is not appropriate in your case you will need to keep a copy inside your Window object. For the rest of this answer I will however assume you pass in a pointer.
With a normal C++ object (not a QObject) you cannot use the SIGNAL/SLOT macro's because they require the use of the slot/signal markers in the class definition.
I see you tried to use the modern method pointer syntax but you made one error. The third parameter needs to be the address of an object of type Some_Class.
QObject::connect(m_button, &QPushButton::clicked, test, &Some_Class::method);
However that is not all, for this to work the signature of clicked has to match with Some_Class::method which it doesn't. clicked has a bool checked parameter.
The construct with the SIGNAL/SLOT macro's allows the slot to have less parameters but this version of connect is more strict and requires a strict match.
You can either add the parameter to method or use a lambda if you have C++11.
QObject::connect(m_button, &QPushButton::clicked, [test] (bool) {
test->method();
});