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How to get first element of QList

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  • D deleted286

    @JKSH if you can look at my last question, the complete code is there. My mind so confused

    JKSHJ Offline
    JKSHJ Offline
    JKSH
    Moderators
    wrote on last edited by JKSH
    #6

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

    @JKSH if you can look at my last question, the complete code is there. My mind so confused

    You need to learn how to use loops.

    Add more debug messages to your code; it might help you see what's happening:

    qDebug() << "I am creating an empty list now.";
    
    QList<int> list;
    
    qDebug() << "My list contains" << list.count() << "items.";
    qDebug() << "My whole list is" << list;
    
    qDebug() << "I am putting an integer into my list now.";
    
    list << inner_data[1].toString().toInt();
    
    qDebug() << "My list contains" << list.count() << "items.";
    qDebug() << "My whole list is" << list;
    

    Qt Doc Search for browsers: forum.qt.io/topic/35616/web-browser-extension-for-improved-doc-searches

    D 1 Reply Last reply
    1
    • JKSHJ JKSH

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

      @JKSH if you can look at my last question, the complete code is there. My mind so confused

      You need to learn how to use loops.

      Add more debug messages to your code; it might help you see what's happening:

      qDebug() << "I am creating an empty list now.";
      
      QList<int> list;
      
      qDebug() << "My list contains" << list.count() << "items.";
      qDebug() << "My whole list is" << list;
      
      qDebug() << "I am putting an integer into my list now.";
      
      list << inner_data[1].toString().toInt();
      
      qDebug() << "My list contains" << list.count() << "items.";
      qDebug() << "My whole list is" << list;
      
      D Offline
      D Offline
      deleted286
      wrote on last edited by
      #7

      @JKSH Thank you but i didnt understand still how can i get items seperately

      JKSHJ 1 Reply Last reply
      0
      • D deleted286

        @JKSH Thank you but i didnt understand still how can i get items seperately

        JKSHJ Offline
        JKSHJ Offline
        JKSH
        Moderators
        wrote on last edited by
        #8

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

        Qt Doc Search for browsers: forum.qt.io/topic/35616/web-browser-extension-for-improved-doc-searches

        D 1 Reply Last reply
        0
        • JKSHJ JKSH

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

          D Offline
          D Offline
          deleted286
          wrote on last edited by
          #9

          @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)
          
          JKSHJ 1 Reply Last reply
          1
          • D 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)
            
            JKSHJ Offline
            JKSHJ Offline
            JKSH
            Moderators
            wrote on last edited by
            #10

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

            and achieve this

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

            Qt Doc Search for browsers: forum.qt.io/topic/35616/web-browser-extension-for-improved-doc-searches

            D 1 Reply Last reply
            0
            • JKSHJ JKSH

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

              and achieve this

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

              D Offline
              D Offline
              deleted286
              wrote on last edited by deleted286
              #11

              @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.HilkJ JKSHJ 2 Replies Last reply
              0
              • D 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.HilkJ Online
                J.HilkJ Online
                J.Hilk
                Moderators
                wrote on last edited by
                #12

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


                Be aware of the Qt Code of Conduct, when posting : https://forum.qt.io/topic/113070/qt-code-of-conduct


                Q: What's that?
                A: It's blue light.
                Q: What does it do?
                A: It turns blue.

                D 1 Reply Last reply
                0
                • D 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)
                  
                  JKSHJ Offline
                  JKSHJ Offline
                  JKSH
                  Moderators
                  wrote on last edited by JKSH
                  #13

                  @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?

                  Qt Doc Search for browsers: forum.qt.io/topic/35616/web-browser-extension-for-improved-doc-searches

                  1 Reply Last reply
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                  • J.HilkJ J.Hilk

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

                    D Offline
                    D Offline
                    deleted286
                    wrote on last edited by
                    #14

                    @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);
                                        }
                    
                                }
                            }
                    
                        }
                    

                    }

                    1 Reply Last reply
                    0
                    • J.HilkJ Online
                      J.HilkJ Online
                      J.Hilk
                      Moderators
                      wrote on last edited by
                      #15

                      @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"
                      }
                      

                      Be aware of the Qt Code of Conduct, when posting : https://forum.qt.io/topic/113070/qt-code-of-conduct


                      Q: What's that?
                      A: It's blue light.
                      Q: What does it do?
                      A: It turns blue.

                      1 Reply Last reply
                      1
                      • Ketan__Patel__0011K Offline
                        Ketan__Patel__0011K Offline
                        Ketan__Patel__0011
                        wrote on last edited by
                        #16

                        @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
                        
                        JKSHJ 1 Reply Last reply
                        0
                        • Ketan__Patel__0011K 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
                          
                          JKSHJ Offline
                          JKSHJ Offline
                          JKSH
                          Moderators
                          wrote on last edited by
                          #17

                          @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.

                          Qt Doc Search for browsers: forum.qt.io/topic/35616/web-browser-extension-for-improved-doc-searches

                          1 Reply Last reply
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