How to get first element of QList

[JKSH]

@suslucoder Did you run the code that I posted? What did you discover?

[deleted286]

@JKSH Yes i run it. I realize that, it add the elements into list by one by.
I move to the definition of list to my header.

run this

                     list << inner_data[1].toString().toInt();
                     qDebug() << "My list contains" << list.count() << "items.";
                     qDebug() << "My whole list is" << list;

and achieve this, by i didnt solve why

My list contains 1 items.
My whole list is (14)
My list contains 2 items.
My whole list is (14, 0)
My list contains 3 items.
My whole list is (14, 0, 1)
My list contains 4 items.
My whole list is (14, 0, 1, 13)

[JKSH]

@suslucoder said in How to get first element of QList:

and achieve this

Good job. Now try list.at(0) again.

[deleted286]

@JKSH it gives me the first item but 4 times.

Why? I didnt understand this. Becauuse if my inner_data[1] size is 4?
How can i solve it?

I expect that giving just this

My list contains 4 items.
My whole list is (14, 0, 1, 13)

[J.Hilk]

@suslucoder
ok, please post the whole function, from opening { to closing }

[JKSH]

@suslucoder said in How to get first element of QList:

@JKSH it gives me the first item but 4 times.

Why?

Because you called list.at(0) 4 times, in a loop.

Loops are used to run code repeatedly. If you don't want a line of code to run repeatedly, then you must put that line outside the loop.

How much do you understand for-loops?

[deleted286]

@J-Hilk

    void MainWindow::Okuma()
 {

QFile file("readJson/deneme.json");


    file.open(QIODevice::ReadOnly | QIODevice::Text);

    QByteArray data = file.readAll();
    QJsonDocument doc = QJsonDocument::fromJson(data);

    QJsonObject root = doc.object();
    QJsonArray tlmtArray = root.value("Telemetri Verileri").toArray();

    for(int i = 0; i < tlmtArray.size(); ++i)
       {
           QJsonObject obj = tlmtArray[i].toObject();
           QJsonArray gps_array = obj.value("GPS").toArray();

    for(int j = 0; j < gps_array.size(); ++j)
        {
            QJsonObject gps_obj = gps_array[j].toObject();

            for(QJsonObject::const_iterator cit = gps_obj.constBegin(); cit != gps_obj.constEnd(); ++cit)
            {
               // qDebug() << cit.key().toStdU16String() <<  ": (";

                QJsonArray inner_data = cit.value().toArray();

                    if(inner_data[0] == "float")
                    {
                       // qDebug() << inner_data[0].toString().toStdU16String() << (0 < inner_data.size()-1 ? "," : "");


                    }


                 if (inner_data[0] == "integer")
                    {
                   //   qDebug() << inner_data[0].toString().toStdU16String() << (0 < inner_data.size()-1 ? "," : "");
                     list << inner_data[1].toString().toInt();

     //                         qDebug() << "My list contains" << list.count() << "items.";
     //                         qDebug() << "My whole list is" << list;

                     qDebug() << list.at(0);
                    }

            }
        }

    }

}

[J.Hilk]

@suslucoder ok, list magically appears, so I assume its a class member, the formatting is horrible,but my guess this is most likely to do copy & past issues in the forum.

Place your qDebug here, and it should work fine

void Okuma ()
{
    
    QFile file("readJson/deneme.json");
    
    
    file.open(QIODevice::ReadOnly | QIODevice::Text);
    
    QByteArray data = file.readAll();
    QJsonDocument doc = QJsonDocument::fromJson(data);
    
    QJsonObject root = doc.object();
    QJsonArray tlmtArray = root.value("Telemetri Verileri").toArray();
    
    for(int i = 0; i < tlmtArray.size(); ++i) {
        QJsonObject obj = tlmtArray[i].toObject();
        QJsonArray gps_array = obj.value("GPS").toArray();
        
        for(int j = 0; j < gps_array.size(); ++j) {
            QJsonObject gps_obj = gps_array[j].toObject();
            
            for(QJsonObject::const_iterator cit = gps_obj.constBegin(); cit != gps_obj.constEnd(); ++cit) {
                
                QJsonArray inner_data = cit.value().toArray();
                
                if(inner_data[0] == "float") {
                    // qDebug() << inner_data[0].toString().toStdU16String() << (0 < inner_data.size()-1 ? "," : "");

                }
                
                if (inner_data[0] == "integer") {
                    //   qDebug() << inner_data[0].toString().toStdU16String() << (0 < inner_data.size()-1 ? "," : "");
                    list << inner_data[1].toString().toInt();
                    
                    //                         qDebug() << "My list contains" << list.count() << "items.";
                    //                         qDebug() << "My whole list is" << list;
                    
                }
            }
        }
    }
    if(!list.isEmpty())
       qDebug() << list.at(0);
    else
      qDebug() << "List has no elements"
}

[Ketan__Patel__0011]

@suslucoder said in How to get first element of QList:

QList<int> index;

try this way

    QList<int> index;
    index.push_back(10);
    index.push_back(20);
    index.push_back(30);
    index.push_back(40);
    index.push_back(50);

    qDebug() << index.at(0); /// Answer Is 10

[JKSH]

@Ketan__Patel__0011 said in How to get first element of QList:

try this way

    QList<int> index;
    index.push_back(10);
    index.push_back(20);
    index.push_back(30);
    index.push_back(40);
    index.push_back(50);

    qDebug() << index.at(0); /// Answer Is 10

OP already figured out the function for obtaining the first element: https://forum.qt.io/post/650999 Their current problem is how to avoid calling it inside a loop.