Re: [Interest] QFileInfoList inheritance producing warnings
-Original Message- From: interest-bounces+eclark=ara@qt-project.org [mailto:interest- bounces+eclark=ara@qt-project.org] On Behalf Of Thiago Macieira Sent: Friday, April 04, 2014 6:04 PM To: interest@qt-project.org Subject: Re: [Interest] QFileInfoList inheritance producing warnings Em sex 04 abr 2014, às 21:20:23, Eric Clark escreveu: I have worked around the warnings by using a QVector instead, but it would still be nice to know why QList is producing all of these warnings... It's not QList, it's MSVC. I assume you added an export clause to your class, right? When you do that, MSVC tries to instantiate all methods in the class, which is what caused it to emit that warning. That makes a lot of sense. Sometimes MSVC can be such a pain in the you know what. Thank you for the response Thiago! Other compilers, more compliant with the C++ standard, won't say anything. I recommend simply silencing the warning. -- Thiago Macieira - thiago.macieira (AT) intel.com Software Architect - Intel Open Source Technology Center ___ Interest mailing list Interest@qt-project.org http://lists.qt-project.org/mailman/listinfo/interest ___ Interest mailing list Interest@qt-project.org http://lists.qt-project.org/mailman/listinfo/interest
Re: [Interest] QFileInfoList inheritance producing warnings
Hello All, I am in the process of creating a class that I would like to inherit QFileInfoList. Four words: Do not do it. QList's destructor not virtual - not meant for inheritance. Guido ___ Interest mailing list Interest@qt-project.org http://lists.qt-project.org/mailman/listinfo/interest
Re: [Interest] QFileInfoList inheritance producing warnings
Op 4 apr. 2014 om 21:38 heeft Guido Seifert warg...@gmx.de het volgende geschreven: Hello All, I am in the process of creating a class that I would like to inherit QFileInfoList. Four words: Do not do it. QList's destructor not virtual - not meant for inheritance. Well, you _can_, as long as you only add methods and no members. Qt does it too, with QQueue and QStack for instance. It can be convenient to add some nice API. André Guido ___ Interest mailing list Interest@qt-project.org http://lists.qt-project.org/mailman/listinfo/interest ___ Interest mailing list Interest@qt-project.org http://lists.qt-project.org/mailman/listinfo/interest
Re: [Interest] QFileInfoList inheritance producing warnings
From: interest-bounces+eclark=ara@qt-project.org [interest-bounces+eclark=ara@qt-project.org] on behalf of Guido Seifert [warg...@gmx.de] Sent: Friday, April 04, 2014 2:38 PM To: interest@qt-project.org Subject: Re: [Interest] QFileInfoList inheritance producing warnings Hello All, I am in the process of creating a class that I would like to inherit QFileInfoList. Four words: Do not do it. QList's destructor not virtual - not meant for inheritance. I am sorry, but are there any Qt developers (or anyone with a better answer or at least an explanation of why not to do it) out there that could answer this question for me? If it was not intended to be inherited, then please explain to me why Qt can do it without problems? As an example, QStringList does exactly this (it is a prefect example of a class that inherits QListQString). Guido ___ Interest mailing list Interest@qt-project.org http://lists.qt-project.org/mailman/listinfo/interest ___ Interest mailing list Interest@qt-project.org http://lists.qt-project.org/mailman/listinfo/interest
Re: [Interest] QFileInfoList inheritance producing warnings
Thank you for the responses that I did get. I still have not solved the problem, but switching to QVector instead of QList seems to have gotten rid of the warnings. Thanks, Eric From: interest-bounces+eclark=ara@qt-project.org [interest-bounces+eclark=ara@qt-project.org] on behalf of Eric Clark [ecl...@ara.com] Sent: Friday, April 04, 2014 3:17 PM To: interest@qt-project.org Subject: Re: [Interest] QFileInfoList inheritance producing warnings From: interest-bounces+eclark=ara@qt-project.org [interest-bounces+eclark=ara@qt-project.org] on behalf of Guido Seifert [warg...@gmx.de] Sent: Friday, April 04, 2014 2:38 PM To: interest@qt-project.org Subject: Re: [Interest] QFileInfoList inheritance producing warnings Hello All, I am in the process of creating a class that I would like to inherit QFileInfoList. Four words: Do not do it. QList's destructor not virtual - not meant for inheritance. I am sorry, but are there any Qt developers (or anyone with a better answer or at least an explanation of why not to do it) out there that could answer this question for me? If it was not intended to be inherited, then please explain to me why Qt can do it without problems? As an example, QStringList does exactly this (it is a prefect example of a class that inherits QListQString). Guido ___ Interest mailing list Interest@qt-project.org http://lists.qt-project.org/mailman/listinfo/interest ___ Interest mailing list Interest@qt-project.org http://lists.qt-project.org/mailman/listinfo/interest ___ Interest mailing list Interest@qt-project.org http://lists.qt-project.org/mailman/listinfo/interest
Re: [Interest] QFileInfoList inheritance producing warnings
Well, you _can_, as long as you only add methods and no members. Qt does it too, with QQueue and QStack for instance. It can be convenient to add some nice API. You can, but you should not. Convenient can also be interpreted as lazy. ;-) I would use a composition approach. Deemed to be more flexible. Why inheritance was used in QQueue and QStack? Simpler code? Better readability? Performance reasons? No idea. If someone can give a reason, it is probably Thiago. :-D Guido ___ Interest mailing list Interest@qt-project.org http://lists.qt-project.org/mailman/listinfo/interest
Re: [Interest] QFileInfoList inheritance producing warnings
-Original Message- From: interest-bounces+eclark=ara@qt-project.org [mailto:interest- bounces+eclark=ara@qt-project.org] On Behalf Of Guido Seifert Sent: Friday, April 04, 2014 3:58 PM Cc: interest@qt-project.org Subject: Re: [Interest] QFileInfoList inheritance producing warnings Well, you _can_, as long as you only add methods and no members. Qt does it too, with QQueue and QStack for instance. It can be convenient to add some nice API. You can, but you should not. Convenient can also be interpreted as lazy. ;-) I would use a composition approach. Deemed to be more flexible. Why inheritance was used in QQueue and QStack? Simpler code? Better readability? I can completely see where you are coming from here Guido, but there is also a very good reason to use inheritance other than being lazy. I mean we are all coders right? Were we not taught that software reuse is a must and NEVER to reinvent the wheel? Yes, composition will give me the same functionality, but it will NOT give me the methods that are provided with the class I inherit. Therefore, if I want to replicate those methods, is it really better to rewrite them all and just call the same method in the object that is now composed instead of inherited? Yes, I can inline these calls and the compiler should be smart enough to inline the calls for performance, but why should I have to rewrite 50 different methods just to call the same exact methods in the class? I would guess that the reason the class was not written with any virtual methods was for performance (and, yes I know that this is a pretty large increase in performance), but I don't need a virtual destructor, nor do I need any virtual methods, I just want to add some extra methods to this particular array to make coding easier on our developers. The Qt developers have done it; therefore, they obviously see the benefit... just trying to figure out why I can't do it... I have worked around the warnings by using a QVector instead, but it would still be nice to know why QList is producing all of these warnings... I really appreciate your feedback by the way! Eric Performance reasons? No idea. If someone can give a reason, it is probably Thiago. :-D Guido ___ Interest mailing list Interest@qt-project.org http://lists.qt-project.org/mailman/listinfo/interest ___ Interest mailing list Interest@qt-project.org http://lists.qt-project.org/mailman/listinfo/interest
Re: [Interest] QFileInfoList inheritance producing warnings
You'd have to show more of your code to make sure what the actual problem is, not just the error message. As it is I can only assume it's a missing C++11 feature that VS 2010 would need to easily re-use the class QList. -Michael. ___ Interest mailing list Interest@qt-project.org http://lists.qt-project.org/mailman/listinfo/interest
Re: [Interest] QFileInfoList inheritance producing warnings
Em sex 04 abr 2014, às 22:58:02, Guido Seifert escreveu: You can, but you should not. Convenient can also be interpreted as lazy. ;-) I would use a composition approach. Deemed to be more flexible. Why inheritance was used in QQueue and QStack? Simpler code? Better readability? Performance reasons? No idea. If someone can give a reason, it is probably Thiago. :-D Homer Simpson rule #1: It was like that when I arrived. -- Thiago Macieira - thiago.macieira (AT) intel.com Software Architect - Intel Open Source Technology Center ___ Interest mailing list Interest@qt-project.org http://lists.qt-project.org/mailman/listinfo/interest
Re: [Interest] QFileInfoList inheritance producing warnings
Em sex 04 abr 2014, às 21:20:23, Eric Clark escreveu: I have worked around the warnings by using a QVector instead, but it would still be nice to know why QList is producing all of these warnings... It's not QList, it's MSVC. I assume you added an export clause to your class, right? When you do that, MSVC tries to instantiate all methods in the class, which is what caused it to emit that warning. Other compilers, more compliant with the C++ standard, won't say anything. I recommend simply silencing the warning. -- Thiago Macieira - thiago.macieira (AT) intel.com Software Architect - Intel Open Source Technology Center ___ Interest mailing list Interest@qt-project.org http://lists.qt-project.org/mailman/listinfo/interest
Re: [Interest] QFileInfoList inheritance producing warnings
Em sex 04 abr 2014, às 16:01:18, Thiago Macieira escreveu: Em sex 04 abr 2014, às 22:58:02, Guido Seifert escreveu: You can, but you should not. Convenient can also be interpreted as lazy. ;-) I would use a composition approach. Deemed to be more flexible. Why inheritance was used in QQueue and QStack? Simpler code? Better readability? Performance reasons? No idea. If someone can give a reason, it is probably Thiago. :-D Homer Simpson rule #1: It was like that when I arrived. Oops, I got the order and the quote wrong. It's rule 3: It was like that when I got here! http://www.aaaugh.com/jokes/homer_simpson.html -- Thiago Macieira - thiago.macieira (AT) intel.com Software Architect - Intel Open Source Technology Center ___ Interest mailing list Interest@qt-project.org http://lists.qt-project.org/mailman/listinfo/interest
