QString::arg Documentation Confusion

[ResistorInTheDark]

This post has to do with my confusion (and potentially the confusion of others) over a particular QString::arg documentation.

I'm not sure where to put this post so I decided to throw it in wiki discussion.

The last example of the section states

QString str;
str = "%1%2%3";
str.arg("Hello", QString::number(20), QString::number(50)); // returns "Hello5020"

I'm rather confused. Shouldn't it either be
str = "%1%3%2"; (line 2)
or
// returns "Hello2050" (line 3)?

I'm sort of inferring that it's supposed to be str = "%1%3%2"; from the point its trying to make. I'm hoping that someone can clarify this for me and perhaps fix it.

Thanks for any clarifications.

[Gojir4]

@ResistorInTheDark Hi,

It looks like a mistake in the documentation. From the context, we can guess that it should be:

String str;
str = "%1%3%2";
str.arg("Hello", QString::number(20), QString::number(50)); // returns "Hello5020"

[ResistorInTheDark]

This post is deleted!

[JonB]

@Gojir4
I believe the format string was correct/intended, and the comment for the output is what was incorrect.... :)

[Gojir4]

@JonB I don't think so. They are demonstrating why you need to be careful when using disordered arguments. See the full chapter. So I stay on my position.

[aha_1980]

Hi @ResistorInTheDark and @Gojir4

thanks for your findings and conclusions. I've prepared a patch to fix the documentation: https://codereview.qt-project.org/238951

Please note that in future you can do discussions about (assumed) bugs here, but the final report should be at bugreports.qt.io, so they are not lost.

Thanks and regards.

[aha_1980]

so, the patch got merged and will be in 5.11.2 or 5.12.

So we can close this topic.

[Gojir4]

@aha_1980 Thanks for haviing handling this. Good job