How to create QList from std::vector

Question

QList::fromStdList allows you to create QList from std::list. But how to create QList from std::vector?

Of course, aside from manual looping:

QList<T> myList;
myList.reserve(vector.size());
for(size_t i = 0, l = vector.size(); i < l; ++i)
    myList << vector[i];

Cyanamide

Wow, never realized they did not have iterator range constructors. That is a surprising lack of functionality. – Arena

@NathanOliver, I am equally just realizing so... I checked their other containers... Astonishingly ridiculous – Loos

Now they have iterator constructors. U can use like QList<T>::fromVector(QVector<T>(vec.begin(), vec.end())) – Immigrate

Answer 1

QVector can be created from a std vector, so you could do this if you want to avoid a loop:

QList<T> myList = QList<T>::fromVector(QVector<T>::fromStdVector(vector));

Of course, this would create an unnecessary copy in the process. Instead of having to write a loop, you could also use a std::copy and back_inserter

QList<T> myList;
myList.reserve(vector.size());
std::copy(vector.begin(), vector.end(), std::back_inserter(myList));

Pratincole

Interestingly, QList::reserve takes an int, while std::vector.size returns an unsigned integral type. Depending on your compiler settings you may get a 'conversion from 'size_t' to 'int', possible loss of data' warning/error. – Wageworker

Note: from Qt's documentation: the generic container classes should be used instead, as stated in doc.qt.io/qt-5/qvector.html#fromStdVector and doc.qt.io/qt-5/containers.html. – Abrasion