Skip to content
  • Categories
  • Recent
  • Tags
  • Popular
  • Users
  • Groups
  • Search
  • Get Qt Extensions
  • Unsolved
Collapse
Brand Logo
  1. Home
  2. Qt Development
  3. General and Desktop
  4. Error using foreach
Forum Updated to NodeBB v4.3 + New Features

Error using foreach

Scheduled Pinned Locked Moved Unsolved General and Desktop
16 Posts 4 Posters 1.5k Views 2 Watching
  • Oldest to Newest
  • Newest to Oldest
  • Most Votes
Reply
  • Reply as topic
Log in to reply
This topic has been deleted. Only users with topic management privileges can see it.
  • F Offline
    F Offline
    frnklu20
    wrote on last edited by
    #3

    Hi,

    yes it is!

    Now i think what is the problem

    foreach(QGraphicsItem *item,scene->items()){
    

    i defined scene as DiagramScene *scene, and when i do scene->items it returns a QGraphicsItem :( i don't know if i can fix it

    1 Reply Last reply
    0
    • F Offline
      F Offline
      frnklu20
      wrote on last edited by
      #4

      is there someway to tell to the computer that the object is member of a subclass too?
      like scene->item is for sure a QGraphicsItem, but is also a DiagramItem that is a subclass of DiagramItem

      i don't know if i was clear

      1 Reply Last reply
      0
      • SGaistS Offline
        SGaistS Offline
        SGaist
        Lifetime Qt Champion
        wrote on last edited by
        #5

        As already suggested, just cast it in the loop. Otherwise you have to add your own method to your class that returns that list of your subclass.

        Interested in AI ? www.idiap.ch
        Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

        1 Reply Last reply
        2
        • F Offline
          F Offline
          frnklu20
          wrote on last edited by
          #6

          how can i do this?

          sorry, i don't what it is

          aha_1980A 1 Reply Last reply
          0
          • F frnklu20

            how can i do this?

            sorry, i don't what it is

            aha_1980A Offline
            aha_1980A Offline
            aha_1980
            Lifetime Qt Champion
            wrote on last edited by
            #7

            @frnklu20

            Could be something like this:

            foreach(QGraphicsItem *item,scene->items()){
                DiagramItem *itempos = (DiagramItem *)item;
                ...
            }
            

            Regards

            Qt has to stay free or it will die.

            1 Reply Last reply
            3
            • F Offline
              F Offline
              frnklu20
              wrote on last edited by
              #8

              oh thanks :))

              1 Reply Last reply
              1
              • SGaistS Offline
                SGaistS Offline
                SGaist
                Lifetime Qt Champion
                wrote on last edited by
                #9

                You also have qgraphicsitem_cast. Take a look at the documentation. There's on additional thing you have to do before using it.

                Interested in AI ? www.idiap.ch
                Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

                1 Reply Last reply
                3
                • F Offline
                  F Offline
                  frnklu20
                  wrote on last edited by frnklu20
                  #10
                                            if(item->type()==DiagramItem::Type && itempos->type()==DiagramItem::Type
                                                    && itempos!=item){
                                            DiagramItem *itempos = (DiagramItem *)item;
                                            DiagramItem *item = (DiagramItem *)item;
                  
                                            DiagramItem *startItem = qgraphicsitem_cast<DiagramItem *>(item);
                                            DiagramItem *endItem = qgraphicsitem_cast<DiagramItem *>(itempos);
                                            Arrow *arrow = new Arrow(startItem, endItem);
                                            arrow->setColor(scene->myLineColor);
                                            item->addArrow(arrow);
                                            itempos->addArrow(arrow);
                                            arrow->setZValue(-1000.0);
                                            scene->addItem(arrow);
                                            }
                  

                  like this? the program keep crashing when i do this

                  aha_1980A 1 Reply Last reply
                  0
                  • SGaistS Offline
                    SGaistS Offline
                    SGaist
                    Lifetime Qt Champion
                    wrote on last edited by
                    #11

                    You're not checking whether these pointers are nullptr.

                    Interested in AI ? www.idiap.ch
                    Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

                    1 Reply Last reply
                    0
                    • F Offline
                      F Offline
                      frnklu20
                      wrote on last edited by
                      #12
                                 if(item->type()==DiagramItem::Type && itempos->type()==DiagramItem::Type
                                       && itempos!=item && item!=nullptr && itempos!=nullptr){
                      

                      like this? the program still crashes

                      but if i remove the lines:

                                   item->addArrow(arrow);
                                   itempos->addArrow(arrow);
                      

                      it doesn't crashes but it doesn't draw a line between the objects neither

                      1 Reply Last reply
                      0
                      • F frnklu20
                                                  if(item->type()==DiagramItem::Type && itempos->type()==DiagramItem::Type
                                                          && itempos!=item){
                                                  DiagramItem *itempos = (DiagramItem *)item;
                                                  DiagramItem *item = (DiagramItem *)item;
                        
                                                  DiagramItem *startItem = qgraphicsitem_cast<DiagramItem *>(item);
                                                  DiagramItem *endItem = qgraphicsitem_cast<DiagramItem *>(itempos);
                                                  Arrow *arrow = new Arrow(startItem, endItem);
                                                  arrow->setColor(scene->myLineColor);
                                                  item->addArrow(arrow);
                                                  itempos->addArrow(arrow);
                                                  arrow->setZValue(-1000.0);
                                                  scene->addItem(arrow);
                                                  }
                        

                        like this? the program keep crashing when i do this

                        aha_1980A Offline
                        aha_1980A Offline
                        aha_1980
                        Lifetime Qt Champion
                        wrote on last edited by
                        #13

                        @frnklu20 Where does it crash exactly? Use a debugger and step through to find the faulty line.

                        Qt has to stay free or it will die.

                        1 Reply Last reply
                        0
                        • F Offline
                          F Offline
                          frnklu20
                          wrote on last edited by
                          #14

                          what i'm trying to do is drawing a line that is QGraphicsItem between 2 objects that already exist using the DiagramScene example form Qt

                          diagramscene.cpp

                          void DiagramScene::mousePressEvent(QGraphicsSceneMouseEvent *mouseEvent)
                          {
                                 
                              if (mouseEvent->button() != Qt::LeftButton)
                                  return;
                          
                              DiagramItem *item;
                              switch (myMode) {
                                     case InsertLine:
                                      line = new QGraphicsLineItem(QLineF(mouseEvent->scenePos(),
                                                                  mouseEvent->scenePos()));
                                      line->setPen(QPen(myLineColor, 2));
                                      addItem(line);
                                      break;
                          }
                          }
                          
                          void DiagramScene::mouseMoveEvent(QGraphicsSceneMouseEvent *mouseEvent)
                          {
                              if (myMode == InsertLine && line != 0) {
                                  QLineF newLine(line->line().p1(), mouseEvent->scenePos());
                                  line->setLine(newLine);
                              } else if (myMode == MoveItem) {
                                  QGraphicsScene::mouseMoveEvent(mouseEvent);
                              }
                          }
                          
                          void DiagramScene::mouseReleaseEvent(QGraphicsSceneMouseEvent *mouseEvent)
                          {
                              if (line != 0 && myMode == InsertLine) {
                                  QList<QGraphicsItem *> startItems = items(line->line().p1());
                                  if (startItems.count() && startItems.first() == line)
                                      startItems.removeFirst();
                                  QList<QGraphicsItem *> endItems = items(line->line().p2());
                                  if (endItems.count() && endItems.first() == line)
                                      endItems.removeFirst();
                          
                                  removeItem(line);
                                  delete line;
                          
                          
                                  if (startItems.count() > 0 && endItems.count() > 0 &&
                                      startItems.first()->type() == DiagramItem::Type &&
                                      endItems.first()->type() == DiagramItem::Type &&
                                      startItems.first() != endItems.first()) {
                                      DiagramItem *startItem = qgraphicsitem_cast<DiagramItem *>(startItems.first());
                                      DiagramItem *endItem = qgraphicsitem_cast<DiagramItem *>(endItems.first());
                                      Arrow *arrow = new Arrow(startItem, endItem);
                                      arrow->setColor(myLineColor);
                                      startItem->addArrow(arrow);
                                      endItem->addArrow(arrow);
                                      arrow->setZValue(-1000.0);
                                      addItem(arrow);  #and here it draws the line
                                      arrow->updatePosition()
                          }
                          }
                          

                          and i what i want to draw a line between 2 objects but not by creating a line with insertline mode

                          mainwindow.cpp

                          void MainWindow::infoItem()
                          {
                              foreach (QGraphicsItem *item, scene->selectedItems()){#the item object is the selected one
                                 if (item->type() == DiagramItem::Type){
                          
                          if(item->data(0)=="Carga"){#carga is type of object
                          CargaDialog *carga=new CargaDialog;
                                        carga->setModal(true);
                          #its a dialog that contains a combo box, an the items of this combo box are the items that are in the screen that are not cargas
                          #and after select an item in the combo box, it will draw a line between the carga and the item selected
                          
                          if(carga->getItem()!="Selecione um barramento" && carga->getItem()!=(item->data(1)).toString()){
                                            #getItem() is a function that return the name of item selected in the combo box
                                            item->setData(4,carga->getItem());
                                            foreach(QGraphicsItem *itempos,scene->items()){
                                                if(itempos->data(1)==carga->getItem())
                                               #i use the data(1) slot of the objects to store the name of each object, so now i looking for the QGraphicsItem that have the same name as the item selected
                                                {
                          
                                                    if(item->type()==DiagramItem::Type && itempos->type()==DiagramItem::Type
                                                            && itempos!=item && item!=nullptr && itempos!=nullptr){
                                                    DiagramItem *itempos = (DiagramItem *)item;
                                                    DiagramItem *item = (DiagramItem *)item;
                          
                                                    DiagramItem *startItem = qgraphicsitem_cast<DiagramItem *>(item);
                                                    DiagramItem *endItem = qgraphicsitem_cast<DiagramItem *>(itempos);
                                                    Arrow *arrow = new Arrow(startItem, endItem);
                                                    arrow->setColor(scene->myLineColor);
                                                    item->addArrow(arrow);#if i remove these two lines, the program doesn't crash but it doesn't draw a line on the screen
                                                    itempos->addArrow(arrow);
                                                    arrow->setZValue(-1000.0);
                                                    scene->addItem(arrow);
                                                    arrow->updatePosition();
                                                    }
                                                }
                          

                          i don't know why this is going on, because it's exactaly the same this that is done in diagramscene.cpp

                          1 Reply Last reply
                          0
                          • SGaistS Offline
                            SGaistS Offline
                            SGaist
                            Lifetime Qt Champion
                            wrote on last edited by
                            #15

                            As already suggested, start your application with the debugger and check the stack trace.

                            Interested in AI ? www.idiap.ch
                            Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

                            1 Reply Last reply
                            1
                            • fcarneyF Offline
                              fcarneyF Offline
                              fcarney
                              wrote on last edited by
                              #16

                              @frnklu20 said in Error using foreach:

                              (DiagramItem *)item;

                              Should this be done this way?

                              DiagramItem *itempos = dynamic_cast<DiagramItem*>(item);
                              // check if itempos is null
                              

                              This gives us some more type safety no?

                              C++ is a perfectly valid school of magic.

                              1 Reply Last reply
                              2

                              • Login

                              • Login or register to search.
                              • First post
                                Last post
                              0
                              • Categories
                              • Recent
                              • Tags
                              • Popular
                              • Users
                              • Groups
                              • Search
                              • Get Qt Extensions
                              • Unsolved