QString::section() NO bug

Gourmet

Here I get QString looking like this:

title = "6 product feature key1:365 days key2:value"

To parse it to elements I use cycle:

for( int i = 0; i < MAXELEMS; i++ )
{
    QString tmp = title.section(QRegExp("\\s+"), i, i);
    qWarning()<<i<<tmp;
//..... further processing
}

Then suddenly see this:

0 6
1 product
2 feature
3 key1:35 //...ooops!!! not key1:365
4 days
5 key2:value

Ok, let's change to

title = "6 product feature key1:375 days key2:value"

Result:

0 6
1 product
2 feature
3 key1:375 //...right
4 days
5 key2:value

Then

title = "7 product feature key1:375 days key2:value"

Oops:

0 7
1 product
2 feature
3 key1:35 //...right
4 days
5 key2:value

And finally:

    QString tmp = title.section(QRegExp("\\s+"), i, i);
    qWarning()<<title;

Prints of:

product feature key1:35 days key2:value // 8-()

That means QString::section cuts off all occurrences equal to required section from source string! This is a bug!
1st - There is nothing about source string change in QString::section() description.
2nd - Why it cuts all occurrences if I need only first one?

I found this in my Android app build with Qt 5.12. Anybody can try check in other OSes.

Christian Ehrlicher

@Gourmet said in QString::section() bug:

There is nothing about source string change in QString::section() description.

QString::section() is const - it can't change the source.
Why not simply use QString::split(QLatin1Char(' '))? Or even QString::splitRef()?

btw: QRegExp is deprecated.

Gourmet

@Christian-Ehrlicher said in QString::section bug:

QString::section() is const - it can't change the source.

But it changes.

@Christian-Ehrlicher said in QString::section bug:

Why not simply use QString::split

The processing is more complex than just split. QString::section() is more useful in my case.

@Christian-Ehrlicher said in QString::section bug:

QRegExp is deprecated

There is nothing about this in Qt docs. As I see only some functions are obsolete but not entire class.

Christian Ehrlicher

@Gourmet said in QString::section() bug:

But it changes.

Please show this to us by providing a small example - you just show snippets.

There is nothing about this in Qt docs.

Hmm: https://doc.qt.io/qt-5/qregexp.html#details

"Note: In Qt 5, the new QRegularExpression class provides a Perl compatible implementation of regular expressions and is recommended in place of QRegExp."

@SGaist: why is \obsolete missing here?

Gourmet

@Christian-Ehrlicher said in QString::section bug:

Please show this to us by providing a small example - you just show snippets.

Sorry, I have no time for experiments. I must fix and release product. May be some time later when I will be free.

J.Hilk

@Christian-Ehrlicher said in QString::section() bug:

why is \obsolete missing here?

I swear last month it was there, because I explicitly looked up which one is obsolete!

J.Hilk

@Gourmet said in QString::section() bug:

Why it cuts all occurrences if I need only first one?

You have to tell it that
https://doc.qt.io/qt-5/qregexp.html#setMinimal

Christian Ehrlicher

@Gourmet said in QString::section() bug:

Sorry, I have no time for experiments. I must fix and release product.

So we can't help you - QString::split() can not change the object - no matter what you tell us.

SGaist

@Christian-Ehrlicher said in QString::section() bug:

@SGaist: why is \obsolete missing here?

Because not all APIs making use of it had replacements. However it's getting nuked in Qt 6.

Gourmet

Finally I have found error in my code. It was hard because of weird processing. QString::split() works fine.

But what about QRegExp - I do not remember why I used it instead of QRegularExpression. May be it looked simpler. This code was redesigned and regular expression was much more complex at beginning.