Connecting SIGNAL to functions

[vyalmicro]

Is there any way to connect SIGNAL to a function which have global scope? Like when button is clicked a function display_error() is evoked? Is it possible or I would need to make a custom class for the widget inheriting from QPushButton adding display_error function in it?
I want to ignore the Object Oriented design as I am more of a C guy.

[wysota]

It is possible in Qt5. In Qt4 you'd have to create a wrapper class to make the call to the function.

[vyalmicro]

A custom class inheriting from QObject who have display_error() function as SLOT would work? like this example:

#include <QObject>
 
class Counter : public QObject
{
    Q_OBJECT
 
public:
    Counter() { m_value = 0; }
 
    int value() const { return m_value; }
 
public slots:
    void setValue(int value);
    void display_error();
 
signals:
    void valueChanged(int newValue);
 
private:
    int m_value;
};

#include <QObject>

class Counter : public QObject
{
    Q_OBJECT

public:
    Counter() { m_value = 0; }

    int value() const { return m_value; }

public slots:
    void setValue(int value);
    void display_error();

signals:
    void valueChanged(int newValue);

private:
    int m_value;
};

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[wysota]

Yes, but I rather meant that the class accepts a function pointer as its constructor's argument and executes the function when it receives a signal. Then you can attach any global function to it.