still compiling (not tested)

helloqube/myitemmodel.cpp

 #include "myitemmodel.h"
 
-MyItemModel::MyItemModel()
+MyItemModel::MyItemModel(QObject* parent) : QAbstractItemModel(parent)
 {
+    root = new TreeItem();
+}
+
+MyItemModel::~MyItemModel(){
+    delete root;
+}
+
+
 
+int MyItemModel::rowCount(const QModelIndex& parent) const {
+    TreeItem* parentItem = getItem(parent);
+    return parentItem->getChildrenCount();
 }
 
+int MyItemModel::columnCount(const QModelIndex &parent) const{
+    return root->columnCount();
+}
+
+
+//Helferfunktion
+TreeItem* MyItemModel::getItem(const QModelIndex& index) const{
+    if (index.isValid()){
+        TreeItem* item = static_cast<TreeItem*>(index.internalPointer());
+        if (item) {
+            return item;
+        }
+    }
+    return root;
+}

helloqube/myitemmodel.h

@@ -2,11 +2,22 @@
 #define MYITEMMODEL_H
 
 #include <QAbstractItemModel>
+#include <treeitem.h>
 
 class MyItemModel : public QAbstractItemModel
 {
+    Q_OBJECT;
 public:
-    MyItemModel();
+    MyItemModel(QObject *parent = 0);
+    ~MyItemModel();
+
+    int rowCount(const QModelIndex& parent = QModelIndex()) const Q_DECL_OVERRIDE;
+    int columnCount(const QModelIndex& parent = QModelIndex()) const Q_DECL_OVERRIDE;
+
+private:
+    TreeItem* root;
+
+    TreeItem* getItem(const QModelIndex &index) const;
 };
 
 #endif // MYITEMMODEL_H

helloqube/treeitem.cpp

@@ -3,6 +3,7 @@
 TreeItem::TreeItem()
 {
     children = QList<TreeItem*>();
+    name = "root";
 }
 
 TreeItem::~TreeItem(){