Il 11/03/21 12:30, Jaroslaw Kobus ha scritto:
Provided I have only one instance of my QHash (so, no detaches are being done), and the only API of the QHash I'm using is: insert(), remove(), contains() and operator[], how long I may rely on the reference to value returned by QHash::operator[]? E.g.:QHash<int, MyValue> hash; hash.insert(1, MyValue(...)); hash.insert(2, MyValue(...)); MyValue &val = hash[1]; hash.remove(2); // May I rely that now my reference is still valid? Wondering, if any internal rehash on remove could copy internal data, so that it invalidates the reference obtained earlier. Assuming that I keep and use this reference only until I explicitly called hash.remove() for the key associated with my reference - may I assume that this reference will be valid?
The quick answer is: in Qt 5 `val` is still valid (modifications of the container only affect iterators/references to the modified elements), while in Qt 6 it's not (modifications of the container invalidates all iterators and references).
So don't rely on that if you want to future-proof your code. (Or, if you really want to rely on that, then switch to std::unordered_map).
HTH, -- Giuseppe D'Angelo | giuseppe.dang...@kdab.com | Senior Software Engineer KDAB (France) S.A.S., a KDAB Group company Tel. France +33 (0)4 90 84 08 53, http://www.kdab.com KDAB - The Qt, C++ and OpenGL Experts
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