[Development] Proposal: Deprecating platforms in Qt 5.6 that don't support lambda

André Somers andre at familiesomers.nl
Fri Feb 20 10:04:31 CET 2015

Bo Thorsen schreef op 20-2-2015 om 09:03:
> Andrés question about how this would change the API is a lot more 
> interesting. I so far haven't seen a single case where someone has 
> described how access to lambdas might improve the API. If they are 
> there, I'd love to see them, because maybe this would teach me 
> something I haven't figured out yet.

One example I could come up with as a potential new API is 
QSortFilterProxyModel. Currently, it requires subclassing to change the 
sort or the filter functions: it supplies protected filterAcceptsRow, 
filterAcceptsColumn and lessThan functions. I think that it would be 
much more convenient if these filters and the comparator could be 
supplied as a function object (a lambda, or a functor, or a std::mem_fn, 
anything callable as a function). While this wasn't all that practical 
in the past, I think C++/11 makes this much more convenient than 

This could of course just be added, instead of replacing. But that would 
mean API bloat. Downside of replacing is of course: you break old code.

I think that if we go over the Qt classes, we'll find more examples of 
where a subclass or a separate function that you need to write could be 
replaced with a more modern API.


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