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QVector <QVector int >> change "inside" vector

I have the following variable in QT:

QVector<QVector <int> > buff_d1;

and I need to change the "inner" vector:

buff_d1.at(i).removeFirst();
buff_d1.at(i).push_back(d1.at(i).at(sample_number));

this throws errors:

    passing 'const QVector<int>' as 'this' argument of 'void QVector<T>::removeFirst() [with T = int]' discards qualifiers [-fpermissive] buff_d2.at(i).removeFirst();
    passing 'const QVector<int>' as 'this' argument of 'void QVector<T>::push_back(const T&) [with T = int]' discards qualifiers [-fpermissive] buff_d1.at(i).push_back(d1.at(i).at(sample_number));

I understand that the "internal" vector is const, so I cannot change it, but what is the job?

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2 answers


The at () function returns a reference const

:

const T & QVector::at(int i) const

and you are trying to change that with the removeFirst () function . You must use the [] operator to change it as it provides a non-const return overload:



T & QVector::operator[](int i)

The same goes for the second error.

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at(int index)

the member function returns a reference to a constant, see the documentation here , so you need to use operator[int index]

non-const to return to be able to modify it.



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