Why this date.fromstring is not working ?

[JonB]

@RahibeMeryem
I don't know whether what @jsulm has just written is correct or not, but https://doc.qt.io/qt-5/qdate.html#fromString-1 says it only accepts date format specifiers, you have date and time. Don't you need QDateTime::fromString(), as in https://doc.qt.io/qt-5/qdatetime.html#fromString-1 ? Then you may want the HH instead of hh (read the doc page for the distinction).

[jsulm]

@JonB said in Why this date.fromstring is not working ?:

what @jsulm has just written is correct or not

It is - just tested.

[JonB]

@jsulm
You tested it with QDate instead of QDateTime, when the OP is passing a date+time value and date+time format? He wants to pass in a date+time with all the formatting for time too, yet he only wants a date returned?

[jsulm]

@JonB @RahibeMeryem Yes, with QDateTime it works with hh also.
Sometimes it's so easy :-)

[JonB]

@jsulm
My point being: if you really only want a QDate back, why would you include the time specifiers in the format string? I'm wondering whether the user intends QDateTime::fromString()...?

[jsulm]

@JonB said in Why this date.fromstring is not working ?:

My point being: if you really only want a QDate back, why would you include the time specifiers in the format string?

You should ask OP, not me

[JonB]

@jsulm
My use of "you" is the "communal" "you", not the "personal" "you" aimed at you :)

[JonB]

@jsulm , @RahibeMeryem
I'm sorry, but it is not the HH vs hh (don't know what you tested for that @jsulm), it is indeed as I said that you need QDateTime for your format:

>>> from PySide2 import QtCore
>>> QtCore.QDate.fromString("17-19-47 2019-12-10" , "hh-mm-ss yyyy-MM-dd")
PySide2.QtCore.QDate(0, 0, 0)
>>> QtCore.QDateTime.fromString("17-19-47 2019-12-10" , "hh-mm-ss yyyy-MM-dd")
PySide2.QtCore.QDateTime(2019, 12, 10, 17, 19, 47, 0, 0)
>>> QtCore.QDate.fromString("17-19-47 2019-12-10" , "HH-mm-ss yyyy-MM-dd")
PySide2.QtCore.QDate(0, 0, 0)
>>> QtCore.QDateTime.fromString("17-19-47 2019-12-10" , "HH-mm-ss yyyy-MM-dd")
PySide2.QtCore.QDateTime(2019, 12, 10, 17, 19, 47, 0, 0)
>>> 

The reason being: if you use QDate, the leading "HH-mm-ss" or whatever will not match against the time, instead it will be treated as literal and therefore the input will fail to match, whatever you do....

[jsulm]

@JonB That's why I wrote "Yes, with QDateTime it works with hh also.".
With QDate it works with HH, but not hh - I tested that:

QDate DATE2 = QDate::fromString("17-19-47 2019-12-10" , "HH-mm-ss yyyy-MM-dd");

And yes, it is correct that one should use QDateTime instead of QDate if there is time and date.

[JonB]

@jsulm
If it works for you with HH plus QDate, could you please explain the output I showed above where it does not work? Thanks.

>>> QtCore.QDate.fromString("17-19-47 2019-12-10" , "HH-mm-ss yyyy-MM-dd")
PySide2.QtCore.QDate(0, 0, 0)

which is an invalid QDate. I am Qt 5.12.2, Ubuntu 19.04.

[J.Hilk]

From my point of view, your both wrong @JonB & @jsulm 😉

the docu only states https://doc.qt.io/qt-5/qdate.html#fromString-1

that only yand Mand dare valid formats everything else is interpreted as a literal character.

and my test confirms it:

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);


    QDate d1 = QDate::fromString("17-19-47 2019-12-10" , "hh-mm-ss yyyy-MM-dd");
    QDate d2 = QDate::fromString("17-19-47 2019-12-10" , "HH-mm-ss yyyy-MM-dd");

    QDate d3 = QDate::fromString("17-19-47 2019-12-10" , "17-19-47 yyyy-MM-dd");
    QDate d4 = QDateTime::fromString("17-19-47 2019-12-10" , "hh-mm-ss yyyy-MM-dd").date();
    qDebug() << d1 << d2 << d3 << d4;

//    return a.exec();
}

Result:
QDate(Invalid) QDate(Invalid) QDate("2019-12-10") QDate("2019-12-10")

[jsulm]

@JonB OK, correction: with QDate it does not work (not with hh and not with HH). I was thinking it does, because my small test application outputs date/time in another place, so it was looking like it was working. Sorry for confusion :-)

[JonB]

@J-Hilk said in Why this date.fromstring is not working ?:

From my point of view, your both wrong @JonB & @jsulm 😉

Interesting, because what you have shown is exactly what I have said! :)

In the case of working

QDate d3 = QDate::fromString("17-19-47 2019-12-10" , "17-19-47 yyyy-MM-dd");

that works only because the literal leading 17-19-47 in the format string matches the input without "placeholder substitutions".

As for the HH vs hh when using QDateTime, that should be irrelevant for the input shown, as per https://doc.qt.io/qt-5/qdatetime.html#fromString-1

hh the hour with a leading zero (00 to 23 or 01 to 12 if AM/PM display)
HH the hour with a leading zero (00 to 23, even with AM/PM display)

as the only difference is to do with "AM/PM", which the input string does not have.

[J.Hilk]

@JonB 😆sorry I got the impression you were arguing for the lower case hhwhich is of course wrong in Date::fromString() missed the other post!