@sayan275 It's also always better to post the relevant code as text and not as image, so others can reproduce it easier.

No sort problem but a basic c(++) problem - you pass the parameters to unzip() by value instead by reference so how should the those variables be updated outside?

There are examples and detailed descriptions on both pages I linked.

Btw. to put my money where my mouth is this is my proposal for this problem. Yes, I'm assuming the format is fixed and search operations won't return -1. If that isn't the case you can add one if to range check the indices. std::ranges::sort(vec, [](QStringView a, QStringView b) { int pos_a = a.lastIndexOf(' '); int pos_b = b.lastIndexOf(' '); int int_a = a.sliced(pos_a).toInt(); int int_b = b.sliced(pos_b).toInt(); return int_a < int_b; }); Do you consider this unreadable? And no, this is not fully optimized either, because it does the same int conversions multiple times, but I consider something like this to be a "good enough starting point" and in-depth optimization is possible if need arises e.g. by caching the conversions or changing the data structure. EDIT Just after posting I realized you can do the QStringView creation right in the params, so even simpler.

@JonB hello, yes I am an beginner in programming. I have like 2 months experience with it. Would you give me an example for my problem please ?

Thank you, that solved my problem :) Now that you wrote it, i remember how it worked in c++. Only one cpp file QVector<gUser> Users; and others extern QVector<gUser> Users; for access. Thanks!

@Turbotroop OK, so: Is the code pasted now currently what you have, exactly? What error do you currently have? Have you acted on the previous comments? For example: although it won't generate a compilation error, it does not make any sense to set up all these boxes or arrays in the main window destructor, does it? Why not in, say, the constructor instead?

Provide a minimal, compilable example where it crashes - everything else is just guessing.

@J-Hilk Thanks, yes I could do that as well.

@CJha said in How to write entire QVector to a binary file?: If it's a copy then I assume it is always going to be the data No, because Qt containers use copy-on-write. See https://doc.qt.io/qt-5/implicit-sharing.html

@Christian-Ehrlicher Thanks! That saves a lot of trouble for me :)

@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...