C++ Singleton Template

# Normally, you want just 1 instance of your Settings class
# Here standart template for this behavior is provided:

-------------------------------header file-----------------------------------
#include "core/config.h"
#include "core/settings.h"

#define $CLASSNAME$Settings ($CLASSNAME$::instance())
#define $CLASSNAME$Settings_writeable (const_cast<$CLASSNAME$*>($CLASSNAME$::instance()))

class $CLASSNAME$ : public Settings
{
public:
    static const $CLASSNAME$ * instance();

    // put here your setting fields

private:
    $CLASSNAME$();
    static $CLASSNAME$ *self;

protected:
    // implementation of pure virtuals from base class
    void settingsChanged();
    void resetGui();
    void flushSettings();
};
-------------------------------source file-----------------------------------
$CLASSNAME$ *$CLASSNAME$::self = 0;

$CLASSNAME$::$CLASSNAME$() :
    Settings("$CLASSNAME$")
{
    TRACE;

    // put here some initialization, probably reading settings from ini files,  using
    // methods from base class

}

const $CLASSNAME$ * $CLASSNAME$::instance()
{
    if(!self)
        self = new $CLASSNAME$;
    return self;
}

void $CLASSNAME$::settingsChanged()
{
    TRACE;
    // this method is called, when user selects Ok in settings dialog -
    // it means, settings in GUI are accepted and have to be applied
}

void $CLASSNAME$::resetGui()
{
    TRACE;
    // this method is called, when user clicks Cancel in settings dialog -
    // it means, settings in GUI are discarded, and class has to fill GUI with old settings
}

void $CLASSNAME$::flushSettings()
{
    TRACE;
    // this method is called, when application terminates, and all settings have
    // to be flushed on disk
}