Re: Weird use of maps.

From	usenet@stegropa.de (Stefan Große Pawig)
Newsgroups	comp.lang.c++
Subject	Re: Weird use of maps.
Date	2019-08-29 20:14 +0200
Organization	Dark Sky
Message-ID	<871rx33kkd.fsf@ID-208667.user.individual.de> (permalink)
References	<qk5vm0$52n$1@dont-email.me> <87ftllb15b.fsf@ID-208667.user.individual.de> <qk791e$a2h$4@dont-email.me>

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[some context restored]

James Kuyper <jameskuyper@alumni.caltech.edu> writes:
> On 8/28/19 9:08 PM, James Kuyper wrote:
>> On 8/28/19 2:22 PM, Stefan Große Pawig wrote:
>>> Is that map of yours stored in another QVariant?
>>>
>> No. The original message map was declared as QMap<QString, QVariant>,
>> and the QVariant values were filled in with part maps of the type
>> QMap<QString, int>. I successfully changed the message map to
> Correction: QMap<QString, QVariant>.

But then, IIUC, that fits the bill: the QMap<QString, QVariant> for the
parts /was/ stored in another QVariant (namely, as the value type of the
message map).

If the code used QVariant::value() to fetch the part map from the message
map, there is no restriction on the type of the part map.  The restriction
only arises if the caller used QVariant::toMap().

Regardless of what the code originally used, maybe the original author
had just scanned the QVariant interface for anything related to maps,
found only the QMap<QString, QVariant> as baked-in return value and then
assumed that this was the only map type that could be stored in a
QVariant?

-Stefan

Thread

Weird use of maps. James Kuyper <jameskuyper@alumni.caltech.edu> - 2019-08-28 09:30 -0400
  Re: Weird use of maps. Jens Kallup <jkallup@web.de> - 2019-08-28 16:22 +0200
    Re: Weird use of maps. James Kuyper <jameskuyper@alumni.caltech.edu> - 2019-08-28 20:46 -0400
  Re: Weird use of maps. Öö Tiib <ootiib@hot.ee> - 2019-08-28 09:00 -0700
    Re: Weird use of maps. "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2019-08-28 14:54 -0700
    Re: Weird use of maps. James Kuyper <jameskuyper@alumni.caltech.edu> - 2019-08-28 20:58 -0400
      Re: Weird use of maps. David Brown <david.brown@hesbynett.no> - 2019-08-29 10:24 +0200
        Re: Weird use of maps. James Kuyper <jameskuyper@alumni.caltech.edu> - 2019-08-29 10:05 -0400
  Re: Weird use of maps. Mike Terry <news.dead.person.stones@darjeeling.plus.com> - 2019-08-28 19:19 +0100
    Re: Weird use of maps. James Kuyper <jameskuyper@alumni.caltech.edu> - 2019-08-28 21:05 -0400
  Re: Weird use of maps. usenet@stegropa.de (Stefan Große Pawig) - 2019-08-28 20:22 +0200
    Re: Weird use of maps. James Kuyper <jameskuyper@alumni.caltech.edu> - 2019-08-28 21:08 -0400
    Re: Weird use of maps. James Kuyper <jameskuyper@alumni.caltech.edu> - 2019-08-28 21:16 -0400
      Re: Weird use of maps. usenet@stegropa.de (Stefan Große Pawig) - 2019-08-29 20:14 +0200
        Re: Weird use of maps. James Kuyper <jameskuyper@alumni.caltech.edu> - 2019-08-29 20:14 -0400
          Re: Weird use of maps. David Brown <david.brown@hesbynett.no> - 2019-08-30 08:28 +0200
            Re: Weird use of maps. Öö Tiib <ootiib@hot.ee> - 2019-08-30 00:15 -0700
          Re: Weird use of maps. Manfred <noname@add.invalid> - 2019-09-13 17:49 +0200
            Re: Weird use of maps. James Kuyper <jameskuyper@alumni.caltech.edu> - 2019-09-13 15:04 -0400
  Re: Weird use of maps. Jorgen Grahn <grahn+nntp@snipabacken.se> - 2019-08-28 19:33 +0000
    Re: Weird use of maps. James Kuyper <jameskuyper@alumni.caltech.edu> - 2019-08-28 21:11 -0400

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