Hi,

I'm trying to subclass QAbstractItemModel so I can add multiple QStandardItemModels and show them in a single QTreeView. Something like:

Qt Code: 
  1. CombinedTreeModel * combined = new CombinedTreeModel (0);
  2. combined ->addStandardItemModel(model1);
  3. combined ->addStandardItemModel(model2);
  4. combined ->addStandardItemModel(model3);
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model1, 2, and 3 are QStandardItemModels and the addStandardItemModel(...) adds the top node of each model to an internal root node in CombinedTreeModel
I used the "simpletreemodel" as an example but instead of using a QStandardItem as the internal rootItem I created a private Root class which inherits from QStandardItem:

Qt Code: 
  1. class Root : public QStandardItem
  2.     {
  3.     public:
  4.         QList<QStandardItem*> child;
  5.  
  6.     };
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I do this because I add the top nodes of the sub-models using model1->item(0) and NOT model1->takeItem(0). I want the original models to keep ownership. I will paste some of the methods I implemented in order to do this below. Unfortunately my code doesn't seem to work when plugging it into a "QTreeView-setModel(combined)". The first node expands just fine (it goes from child0->child1->child2->child3) but the other 2 top-nodes throw an ASSERT when i try to expand child2:
File: global\qglobal.cpp
Line: 2090

ASSERT: "i > -1" in file itemviews\qtreeview.cpp, line 3038
The ASSERT appears to occur when the method "parent(...)" exits.

Does anybody know what I might be doing wrong or if I'm doing something that isn't possible at all.

Qt Code: 
  1. int CombinedTreeModel::rowCount(const QModelIndex &parent) const
  2. {
  3.     QStandardItem *item = getItem(parent);
  4.     if (item == rootItem) {
  5.         return rootItem->child.size();
  6.     }    
  7.     return item->rowCount();
  8. }
  9.  
  10. int CombinedTreeModel::columnCount(const QModelIndex &parent) const
  11. {
  12.     return 1;
  13. }
  14.  
  15. bool CombinedTreeModel::rootContains(QStandardItem *child) const
  16. {
  17.     for (int i = 0; i < rootItem->child.size(); i++) {
  18.         if (child == rootItem->child.at(i)) {
  19.             return true;
  20.         }
  21.     }
  22.     return false;
  23. }
  24.  
  25. QVariant CombinedTreeModel::data(const QModelIndex &index, int role) const
  26. {
  27.     if (!index.isValid())
  28.         return QVariant();
  29.  
  30.     if (role != Qt::DisplayRole && role != Qt::EditRole)
  31.         return QVariant();
  32.  
  33.     QStandardItem *item = getItem(index);
  34.  
  35.     return item->data(index.column());
  36. }
  37.  
  38. Qt::ItemFlags CombinedTreeModel::flags(const QModelIndex &index) const
  39. {       
  40.     return getItem(index)->flags();
  41. }
  42.  
  43. QModelIndex CombinedTreeModel::parent ( const QModelIndex & index ) const
  44. {
  45.     if (!index.isValid())
  46.         return QModelIndex();
  47.  
  48.     QStandardItem *childItem = getItem(index);
  49.     QStandardItem *parentItem = childItem->parent();    
  50.  
  51.     // parentItem == rootItem
  52.     if (rootContains(childItem)) {    
  53.         return QModelIndex();        
  54.     }
  55.  
  56.     return createIndex(parentItem->row(), 0, parentItem); 
  57. }
  58.  
  59. QModelIndex CombinedTreeModel::index( int row, int column, const QModelIndex & parent ) const
  60. {
  61.     if (parent.column() > 0)
  62.         return QModelIndex();
  63.  
  64.     QStandardItem* parentItem = getItem(parent);
  65.     QStandardItem* childItem ;
  66.  
  67.     if (parentItem == rootItem) {       
  68.        childItem = rootItem->child.at(row);
  69.     } else {
  70.        childItem = parentItem->child(row);
  71.     }
  72.  
  73.     if (childItem)
  74.         return createIndex(row, column, childItem);
  75.     else
  76.         return QModelIndex();
  77. }
  78.  
  79. QStandardItem *CombinedTreeModel::getItem(const QModelIndex &index) const
  80. {
  81.     if (index.isValid()) {
  82.         QStandardItem *item = static_cast<QStandardItem*>(index.internalPointer());
  83.         if (item) return item;
  84.     }
  85.     return rootItem;
  86. }
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