copying a std::vector to a qvector

Question

I tried copy content of one vector to a QVector using the following

std::copy(source.begin(), source.end(), dest.begin());

However the destination QVector still is empty.

Any suggestions ?

Use [`QVector::fromStdVector`](http://qt-project.org/doc/qt-4.8/qvector.html#fromStdVector) — Praetorian, Aug 08 '13 at 15:15

score 23 · Accepted Answer · edited Mar 09 '17 at 20:36

23

Look at:

std::vector<T> QVector::toStdVector () const

QVector<T> QVector::fromStdVector ( const std::vector<T> & vector ) [static]

From docs

edited Mar 09 '17 at 20:36

Donald Duck

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answered Aug 08 '13 at 15:15

trompa

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tried that. as `MyQvector.fromStdVector(MyStedVector);` still the qvector is empty – Rajeshwar Aug 08 '13 at 15:21
2

@Rajeshwar: because it static method, try: MyQvector = QVector::fromStdVector( MyStedVector ); – user1837009 Aug 08 '13 at 15:37

score 8 · Answer 2 · edited Jun 11 '20 at 18:53

8

'fromStdVector' has been explicitly marked deprecated recently. Use following code:

std::vector<...> stdVec;

// ...       

QVector<...> qVec = QVector<...>(stdVec.begin(), stdVec.end());

edited Jun 11 '20 at 18:53

Sandro4912

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answered Feb 26 '20 at 16:37

Hadi Navapour

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I really don't see why QT team has deprecated this function. it seems quite useful and more easy to write in my mind ... – Kafka Oct 20 '20 at 13:46

score 5 · Answer 3 · edited Nov 22 '16 at 19:37

5

If you are creating a new QVector with the contents of a std::vector you can use the following code as an example:

   std::vector<T> stdVec;
   QVector<T> qVec = QVector<T>::fromStdVector(stdVec);

edited Nov 22 '16 at 19:37

NotJo

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answered Aug 08 '13 at 15:16

dunc123

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score 2 · Answer 4 · edited Apr 03 '18 at 19:30

As the other answers mentioned, you should use the following method to convert a QVector to a std::vector:

std::vector<T> QVector::toStdVector() const

And the following static method to convert a std::vector to a QVector:

QVector<T> QVector::fromStdVector(const std::vector<T> & vector)

Here is an example of how to use QVector::fromStdVector (taken from here):

std::vector<double> stdvector;
stdvector.push_back(1.2);
stdvector.push_back(0.5);
stdvector.push_back(3.14);

QVector<double> vector = QVector<double>::fromStdVector(stdvector);

Don't forget to specify the type after the second QVector (it should be QVector<double>::fromStdVector(stdvector), not QVector::fromStdVector(stdvector)). Not doing so will give you an annoying compiler error.

copying a std::vector to a qvector

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