How to use wrapper class?

I have a QgraphicsScene which contains many QGraphicsItem. I am reading line, arc and circle's co-ordinates from a file and storing them in a map and when time comes to draw them, I iterate over that map and give those co-ordinates to respective Qt's Api.
But the problem is that, the symbol which is getting generated is not fully selectable.
Means if a symbol is created by let's say 4 lines, 1 arc and 1 circle. Then if I click on a particular line, then only that line gets selected. Or that particular arc gets selected.
But I am expecting, on clicking, the full symbol should be selected.

For that I was suggested to use wrapper class. But not understanding how to use that ?

Here is my structure:

class mySymbol 
{
    struct Line {
       std::tuple<int, int, int, int> line;
    };
   struct Arc {
       std::tuple<int, int, int, int, int, int> arc;  
    };
  struct Circle {
       std::tuple<int, int, int> circle;
   };

  struct Rect 
  {
      std::vector<Line> allLines;
      std::vector<Arc> allArcs;
      std::vector<Circle> allCircles;
  }

std::map<std::string, Rect> allShapes;
}

DrawShapes.h

class DrawShapes
{
  void createSymbol(map<std::string, Rect>);
}

DrawShapes.cpp

void DrawShapes :: createSymbol(map<std::string, Rect> allShapes)
{
   QGraphicsItemGroup * parentGroup = new QGraphicsItemGroup;
   for (auto iter = allShapes.begin(); iter != allShapes.end(); ++iter)
  {
     if (iter->second.allLines.size() > 0) 
      {
         for (unsigned int i = 0; i < iter->second.allLines.size(); i++) 
           {
              // getting 4 co-ordinates of line as first,second,third and fourth
              myLine* line = new myLine(first,second,third,fourth);
              line->DrawLine();
              parentGroup->addToGroup(line);
              scene->addItem(static_cast<QGraphicsLineItem*>(line));
           }
     }
     // same logic for arc and circle 
}      

myLine.h

class myLine: public QGraphicsLineItem
{
public:
    myLine();
    myLine(int x1,int y1,int x2 ,int y2,QGraphicsItem *parent = nullptr)
        : QGraphicsLineItem(x1,y1,x2,y2,parent)
    {}
    void DrawLine();
};     

myLine.cpp

void myLine::DrawLine()
{
    this->setPen(QPen(QColor("blue"), 1));
    this->setFlag(QGraphicsItem::ItemIsSelectable);
}