On Monday, 2015-02-09, 16:52:39, PCMan wrote: > On Mon, Feb 9, 2015 at 7:03 AM, Kevin Krammer <kram...@kde.org> wrote: > > On Monday, 2015-02-09, 04:07:04, PCMan wrote: > > > OK, a list of main features I plan to use. > > > 1. auto > > > 2. nullptr > > > 3. new range based for() loop for iterating over containers > > > > One thing to keep looking out for with this is to be very careful when > > applying it on Qt containers (can trigger detach(), i.e. deep copy). > > > Thank you for the info. > > I did not expect that! > Previously I planed to use Qt containers with ranged for loop. :-( > Sounds like a bad idea, then.
You can use foreach() for Qt containers and ranged-for for STL containers. They are potentially bad for the other use case, since they were designed with their respective containers in mind. foreach() makes a copy of the container, which is no problem for a Qt container since it is reference counted, but it leads to an actual copy on an STL container. ranged-for calls being/end of a container, which are only const if the container itself is const. On a non-const Qt container, the invocation of non-const methods leads to detach(). If the container has a reference count > 1, this will lead to an actual copy. The easiest way is to use the respective convenience "for", but ranged-for can be used for Qt containers if they are either ensured a reference count of 1 or the expression passed to the ranged-for is a const type. > > > 5. smart pointers > > > > Could also be using Qt's smart pointer in most cases. > > True, but if the standard library provides the same facilities, it's good > to use it. > For code not related to UI, using only the standard library can make it > reusable in non-Qt projects. > That's the point of this proposal. Ah, I see. I was thinking about code involving Qt :-) > > 6. move semantics/r value reference > > > > > 7. override keyword (optional) > > > > Can always use Q_DECL_OVERRIDE but override is of course shorter. > > True, but C++ code full of macros really looks alien. > If we don't plan to support legacy systems that have a broken c++ compiler, > it's safe to use real C++ keyword here. Oh, I agree, just pointing out an option. Cheers, Kevin -- Kevin Krammer, KDE developer, xdg-utils developer KDE user support, developer mentoring
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