[Development] QList

Jason H jhihn at gmx.com
Mon May 29 14:53:24 CEST 2017


> Sent: Thursday, May 25, 2017 at 7:03 PM
> From: "André Somers" <andre at familiesomers.nl>
> To: "Christoph Feck" <cfeck at kde.org>
> Cc: development at qt-project.org
> Subject: Re: [Development] QList
>
> Hi,
> 
> Sent from my phone, please excuse my brevity
> 
> > On 25 May 2017, at 18:40, Christoph Feck <cfeck at kde.org> wrote:
> > 
> >> On 25.05.2017 13:53, André Somers wrote:
> >> Op 25/05/2017 om 12:38 schreef Konstantin Tokarev:
> >>> Other problem, that IMO is more serious, is that Qt *requires* user to use QList,
> >>> by returning or taking it as and argument in various places. That's almost only
> >>> reason why I use QList in my code[*].
> >>> 
> >>> If Qt 6 APIs are changed from QList to QVector, lots of user code dealing with
> >>> this APIs will break, unless QList will become an alias of QVector.
> >>> 
> >>> [*] And, fwiw, almost only reason I use QString, but that's off-topic here
> >>> 
> >> I think you bring up a good point there. Would not the best way out be
> >> to fix exactly this problem? If these functions would not return a
> >> container, but some type of view into such a container, that would leave
> >> users free to choose the type of container they need for their job
> >> instead of being forced into the direction Qt choose for its API. A view
> >> might take the form of a pair of iterators, a range, or perhaps even
> >> some specialized class that basicaly wraps a pair or iterators and that
> >> provides convenience functions to/from the Qt containers.
> > 
> > If you only return a view to the container, then if the container is modified, the return value is no longer valid. Returning a full container (referenced, with copy-on-write semantics) will not have this problem.
> 
> Sure, but do you always or even most of the time need that feature? If not, why always pay for it? And it would be easy to turn it into a container when needed, but then you can choose the most appropriate for your task instead of always getting a QList (now) or a QVector (Qt6?)




I wonder how gsl::span plays into this. I just learned about span, quick seems to be wet we need here?












 
> André
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