Error while calling installing singleton class Qt Message Handler member function

[d_stranz]

From the docs:

typedef QtMessageHandler

This is a typedef for a pointer to a function with the following signature:

void myMessageHandler(QtMsgType, const QMessageLogContext &, const QString &);

The important words are pointer to a function, not pointer to a MEMBER function. This typically means a stand-alone function, but in your case you might be able to use a static member function of your Log class.

However, I would turn your design inside-out. Implement the message handler as a stand-alone function, but inside the handler, relay the message to the singleton's handler:

class Log : public QObject
{
    Q_OBJECT
public:
    //class member declaration 
 
    static Log& ReturnInstance()
    {
       static Log Log_obj;   //The only Log object that will be used
       return Log_obj;
    }
    void myMessageHandler(QtMsgType type,QMessageLogContext &context,const QString &msg);
 
    private:
    //some member variable declartion
    QFile m_file;
 
};
 
static void theMessageHandler(QtMsgType type,QMessageLogContext &context,const QString &msg)
{
    Log & log = Log::ReturnInstance();
    log.myMessageHandler( type, context, msg );
}
 
#include "mainwindow.h"
#include <QApplication>
#include "logger.h"
 
int main(int argc, char *argv[])
{
    qInstallMessageHandler( theMessageHandler );    //<------ The former error
    QApplication a(argc, argv);
    MainWindow w;
    w.show();
 
    return a.exec();
}

class Log : public QObject
{
    Q_OBJECT
public:
    //class member declaration 
 
    static Log& ReturnInstance()
    {
       static Log Log_obj;   //The only Log object that will be used
       return Log_obj;
    }
    void myMessageHandler(QtMsgType type,QMessageLogContext &context,const QString &msg);

    private:
    //some member variable declartion
    QFile m_file;
 
};

static void theMessageHandler(QtMsgType type,QMessageLogContext &context,const QString &msg)
{
    Log & log = Log::ReturnInstance();
    log.myMessageHandler( type, context, msg );
}

#include "mainwindow.h"
#include <QApplication>
#include "logger.h"
     
int main(int argc, char *argv[])
{
    qInstallMessageHandler( theMessageHandler );    //<------ The former error
    QApplication a(argc, argv);
    MainWindow w;
    w.show();
    
    return a.exec();
}

To copy to clipboard, switch view to plain text mode 

[Ahmed Abdellatif]

Thanks a lot