@Mquaza said in QPainter drawRects without draging a line behind: How do you make it so, that 2 rectangles are moving across the scene? I would say change their coordinates?

@raven-worx Thank you for this answer. In fact I already found this example but wouldn't this be a problem if my Person class is in a vector?

@SGaist Thank you.

@JonB said in What should I do to solve this error in Qvector?: if you are saying that a properly-compiled 64-bit now bombs out in the same way as 32-bit at what we think is only half a gig of so of memory on a machine with plenty of free RAM, earlier I was doing mistake while creating 64 bit application version. I am using visual studio while creating 64 bit application I was just copied all setting of 32 bit application, So That in Solution platform it was showing x64 but it was creating 32 bit executable file. I created 64 bit application version, which is save very large amount of data in RAM.

@Yash001 said in which container (Qvector or QList) is good to use for insert, delete, and access the last element.: I am adding data point at last position of container, and only accessing the last element of container. So which is better container? It's what we call Last In First Out ( LIFO) queue. So QStack seems an obvious candidate. QStack inherits from QVector.

@mrjj good catch ^^

@mrjj Thank you for your tip. Its great help for a QT and C++ beginner. I'll try to implement the logic you mentioned.

@SGaist does the same as copy at the end. I did not trust vec=vec. So I ended up doing it "Manually". Will try to go back to native c++ calls/overload/ once I know I dont have other bugs influencing the source...

@kshegunov @mrjj Thanks for your explanation. Finally I figured out that the problem lay in the signal QGraphicsScene::changed I used. I learned about this signal in an OpenGL example in Qt. By using it I was trying to update my wave soon after its last update, however this signal could also be triggered by changing axis range or window resize, which would probably cause the crash for I didn't consider thread safety and synchronization under this condition. So I defined a custom signal function and now the problem is solved.

@elfring said in Returning C++ references from more programming interfaces?: For example, why should Qt provide extensions that break encapsulation and increase the risk of errors? I suggest to use algorithms which can work together with container classes at more source code places. You did not address any of the concerns. You only added suggestions. That is not acceptable. You must only submit ideas/proposals that don't break encapsulation.

I got it done by the below code QFileInfoList filelistinfo = dir.entryInfoList(); for(const QFileInfo &fileinfo: filelistinfo) imagePath.push_back(fileinfo.absoluteFilePath()); std::sort(imagePath.begin(), imagePath.end(), [](const QString & a, const QString & b) -> bool { return QFileInfo(a).baseName().toInt() < QFileInfo(b).baseName().toInt(); }); qDebug()<<imagePath;

Related issue: https://bugreports.qt.io/browse/QTBUG-49250

Thanks @karlheinzreichel Originaly I have data called Sample, to save it I save it as a QVector<double> const Value. for(int iSamples=0;iSamples<_pSampleProcessing->getRawDataVector().size();iSamples++) { xDataVector.append(_pSampleProcessing->getRawDataVector().at(iSamples).getX()); yDataVector.append(_pSampleProcessing->getRawDataVector().at(iSamples).getY()); } I dont think so, because If it would be overloaded I might get an error, because I tried it to save it as a Sample before. So saving as a double seems possible.

Hello guys. Thanks for your answerS. The "error" was simple, stupid. In fact the _manageOrderedTable is an instance of a class called ManageOrderedTable which inherits from QTableWidget. In this class, there's a method called fillAll and I called setColumnCount() from there. Bad idea. When I call this method from upon the for loop, everything is fine. I don't understand why. I could understand if setColumnCount() were called too late, but in this case I should have a segfault, trying to call a cell that doesn't exist. Well, I don't really understand why but now it works... Tank you for your help, Patrick.

that is wrong way of doing it try this: QByteArray bytesArray QDataStream out(&bytesArray ,QIODevice::WriteOnly); out << someVector; //saves it //////////////////////////////////////////////////////////////////// QDataStream in(bytesArray); QVector<qreal> otherVector; in >> otherVector; //load Please note that qreal is only 99.9% safe when saving to stream and sending it around to programs built with other versions of Qt. use QVector<double> instead

Hi When you insert pointers in Qvector, all it ever will delete is the pointer as it would be unsafe for it to delete the object pointed too as it is outside the vector. If you declare it as not pointer QVector<SellInfo> Then the SellInfo struct lives in the vector and will be deleted when QVec is. Deleting a SellInfo would never delete "box" as it will not call box destructor. (its a pointer) A good rule is that you bring into the world with new, should be removed with delete. But in Qt, many of the Wigets takes ownership of childs and you do not need to call delete on them.

@SGaist Thank you :) This solved my problem.

Thanks. Fixed. How just got rid of that damn pointer.

Ok fixed.

@Wieland OK... So, you're replacing all the next lines in the string list to spaces and then splitting the strings by spaces. That's pretty neat. Thank you very much. This solution works perfectly for me. I upvoted all your answers. Thank you, Wieland.