Singleton QDateTime Issues

Simof

Is it possible to make singleton class that inherits from QDateTime?

I would like use the same QDateTime instance insted of currentTime in all my classes.

For exemple:

#ifndef CALENDAR_H
#define CALENDAR_H

#include <QDateTime>

#include <QObject>

class Calendar : public QDateTime
{
    Q_OBJECT

public:

    virtual ~Calendar() {}

    static Calendar & GetInstance()
    {
        static Calendar instance;
        return instance;
    }

private:
    explicit Calendar() : QDateTime() {}

};

#endif // CALENDAR_H

This code produce a lots of MOQ errors

CP71

@Simof
Hi,
try to remove Q_OBJECT

Christian Ehrlicher

And what do you think you gain with this class??

Simof

@Christian-Ehrlicher said in Singleton QDateTime Issues:

And what do you think you gain with this class??

I would include this class in all widgets and use this instead of System Clock

QString dateTimeStr = Calendar::GetInstance().toString("\"yyyy-MM-dd hh:mm\"");
dateTimeLbl = new QLabel(dateTimeStr);

jsulm

@Simof You should read https://doc.qt.io/qt-5/qdatetime.html#QDateTime

jsulm

@Simof Why don't you simply use static https://doc.qt.io/qt-5/qdatetime.html#currentDateTime instead of introducing a singleton?!

Simof

@CP71 said in Singleton QDateTime Issues:

@Simof
Hi,
try to remove Q_OBJECT

Now it works correctly, thanks

Simof

@jsulm said in Singleton QDateTime Issues:

@Simof Why don't you simply use static https://doc.qt.io/qt-5/qdatetime.html#currentDateTime instead of introducing a singleton?!

Can I define a static QDateTime in main mainwindow and use it in all widgets included inside itself?

jsulm

@Simof said in Singleton QDateTime Issues:

Can I define a static QDateTime in main mainwindow and use it in all widgets included inside itself?

Why do you need a static QDateTime? What is your use case?

CP71

@Simof
Hi
As @jsulm says , you don't need a singleton and static class to do this if you have to do something else that we don't know.
To do this you can write QString text = QDateTime::currentDateTime().toString(""yyyy-MM-dd hh:mm""); without declare new class o singleton class.

Simof

@CP71 said in Singleton QDateTime Issues:

@Simof
Hi
As @jsulm says , you don't need a singleton and static class to do this if you have to do something else that we don't know.
To do this you can write QString text = QDateTime::currentDateTime().toString(""yyyy-MM-dd hh:mm""); without declare new class o singleton class.

My application works on embedded device and the system time is not reliable so I would use a RTC (Real Time Clock IC) such a main clock.

I could use QDateTime::currentDateTime().toString(""yyyy-MM-dd hh:mm"") only if I can set my system time equal to RTC time but I don't know if it's possible

JonB

@Simof
So don't use raw currentDateTime. If you don't want to repeatedly read RTC (I don't do embedded, maybe that is expensive or inconvenient?), read it once and get currentDateTime() at same time, calculate offset difference, use that adjustment amount to currentDateTime() from then onward?