How to insert different arrays into a QVector.

Shankar B

I have two arrays
example:
a[3]={1,2,3};
b[5]={4,5,6,7,8};

i want to insert into QVector . Later i need to retrieve each element of respective arrays from the Qvector. I am getting the size of the vector as 2 but I am unable to retrieve each element of array. Any help will be most appreciated.

J.Hilk

Hi @Shankar-B
and welcome,

can you share some more code, with what you already did, and what you actually want :)

Pl45m4

@Shankar-B

How do you insert the values into your QVector? With push_back(val)?

If you need array "a" and "b" in one container as such, try a 2D-Vector or Vector of Vectors.

You can access them by using

QVector< QVector<int> > vec;
// fill vector
// [...]
// Access elements
for(int i = 0; i < vec.size(); i++)
{
  for(int j = 0; j = vec.at(i).size(); j++)
  {
       qDebug() << vec.at(i).at(j);
  }
}

Shankar B

int a[3]={1,2,3};
int b[5]={4,5,6,7,8};

    QVector<int> vec;
    vec.push_back(a[3]);
     vec.push_back(b[5]);

     int s = vec.size();
         for (int i=0;i<s;i++)
         {
             qDebug() << vec[i][i];

         }

Since am new to this i am not getting how to access each element of the corresponding array when they merged in to vector. Above lines of code i was trying these thing.

JonB

@Shankar-B

vec[i][i];

Use of i for both indexes is wrong! And will indeed only print out first 2 elements of the arrays in the 2-element vector.

You want more like (untested)

         for (int i=0;i<s;i++)
             for (int j = 0; j < vec[i].size(); j++)
             {
                 qDebug() << vec[i][j];
             }

Further:

    vec.push_back(a[3]);
     vec.push_back(b[5]);

This is only pushing one element from each a/b array into the vector. I think you're wanting to push whole arrays, like vec.push_back(a)? In which case declaration QVector<int> vec will be wrong....?

Shankar B

int a[3]={1,2,3};
int b[5]={4,5,6,7,8};

   QVector< QVector<int> > vec;
    vec.push_back(a);
     vec.push_back(b);



         for (int i=0;i< vec.size();i++)
         {
             for(int j = 0; j = vec.at(i).size(); j++)
              {
                   qDebug() << vec.at(i).at(j);
              }

         }

         }

when ever am compiling these thing am getting below error.

D:\Qt Projects\Testingexample\mainwindow.cpp:41: error: no matching function for call to 'QVector<QVector<int> >::push_back(int [3])'
vec.push_back(a);

J.Hilk

@Shankar-B
well, yes, you're mixing and matching at will.

int a[3]={1,2,3}; != QVector<int>

I would suggest not to use pure c arrays, use the vector container for it. If you need to pass the raw array around later on, you can get that by calling data() of the container

QVector<int> a ={1,2,3};
    QVector<int> b ={4,5,6,7,8};

    QVector<QVector<int> > vec;
    vec.push_back(a);
    vec.push_back(b);

    int s = vec.size();
    for (int i=0;i<s;i++)
    {
        auto element = vec.at(i);
        for(int j(0); j < element.size(); j++)
            qDebug() << i << element[j];
        qDebug () << endl;

    }

Pl45m4

@Shankar-B

Because you have a matrix-like vector now, you need to change push_back(x) to something like:

QVector< QVector<int> > vec;

// static indices not a clean solution but just to demontrate
vec.at(0).push_back(i);
vec.at(1).push_back(j);

But you need to interate through your input arrays first.

Shankar B

I tried the above response from J.Hilk and it is working fine. Thanks to all from their prompt replies which helped me in resolving this issue.

J.Hilk

@Shankar-B great don't forget to use the topic tools to set the topic to solved :)

Shankar B

How to convert const QVector<quint32> to vector<int>.
example:
std::vector<int> l_sensorAddressList= static_cast<quint32>p_sensorAddressList.toStdVector();

JonB

@Shankar-B
You raised a dedicated topic https://forum.qt.io/topic/107950/how-to-convert-const-qvector-quint32-to-vector-int for this question. That's where it belongs, not as a post in the topic too.