Subclassing QAbstractItemModel - struggling with createIndex()/internalPointer()

Yes, I never implemented this. I think it requires special support by
PythonQt.

On Fri, Nov 8, 2019 at 3:24 PM Max galicarnax@users.sourceforge.net wrote:

I had no trouble creating QTreeView and connecting it to
QAbstractTableModel on the Python side of PythonQt. Now I need to create
a custom model by subclassing QAbstractItemModel, and I just can't make
it working. Help is appreciated.

Basically, the problem is with the createIndex() method, which
accepts row/column and a pointer to a custom tree-item object. Since in
Python there are no pointer, I tried passing just the object itself (as
usual), but it failed with errors like this one:

ValueError: Could not find matching overload for given arguments:
(1, 0, <gui.treeitem object="" at="" 0x00000232aaa3b550="">)
The following slots are available:
createIndex(int row, int column, quintptr id) -> QModelIndex
createIndex(int row, int column, void data) -> QModelIndex
createIndex(int row, int column) -> QModelIndex</gui.treeitem>

So I thought maybe I can use the first suggestion with quintptr, and
passed not the python object, but (presumably) its address with id(...).
That made this error go away, but then calling
QModelIndex.internalPointer() always returns None.

Below is the minimal example to run from PythonQt. There error points are
indicated in comments.

By the way, I tried to use this very code with PyQt5 (with different
imports, of course, and also adding QApplication for the event loop,
which I don't need in PythonQt as it is handled in C++ side), and it does
work there.

```
from PythonQt.QtCore import QAbstractItemModel, QModelIndex, Qt
from PythonQt.QtGui import QTreeView

class TreeItem(object):
def init(self, content, parentItem):
self.content = content
self.parentItem = parentItem
self.childItems = []

def appendChild(self, item):
self.childItems.append(item)

def child(self, row):
return self.childItems[row]

def childCount(self):
return len(self.childItems)

def columnCount(self):
return 1

def data(self, column):
if self.content != None and column == 0:
return self.content

return None

def parent(self):
return self.parentItem

def row(self):
if self.parentItem:
return self.parentItem.childItems.index(self)
return 0

class NodeTree(QAbstractItemModel):
def init(self, parent, data):
QAbstractItemModel.init(self)
self.rootItem = TreeItem(-1, None)
self.parents = {0: self.rootItem}
self.setupModelData(self.rootItem, data)

def setupModelData(self, root, data):
for el in data:
if isinstance(el, list):
item = TreeItem("Node", root)
self.setupModelData(item, el)
else:
item = TreeItem(el, root)
root.appendChild(item)

def rowCount(self, parent=QModelIndex()):
if parent.column() > 0:
return 0
if not parent.isValid():
p_Item = self.rootItem
else:
p_Item = parent.internalPointer()
return p_Item.childCount()

def columnCount(self, parent=QModelIndex()):
return 1

def data(self, index, role):
if not index.isValid():
return None

item = index.internalPointer()
if role == Qt.DisplayRole:
  return item.data(index.column())
if role == Qt.UserRole:
  if item:
    return item.content
return None

def headerData(self, column, orientation, role):
if (orientation == Qt.Horizontal and
role == Qt.DisplayRole):
return "Content"
return None

def index(self, row, column, parent):
if not self.hasIndex(row, column, parent):
return QModelIndex()

if not parent.isValid():
  parentItem = self.rootItem
else:
  parentItem = parent.internalPointer()

childItem = parentItem.child(row)
if childItem:
  return self.createIndex(row, column, childItem)   # ====  ERROR

======
else:
return QModelIndex()

def parent(self, index):
if not index.isValid():
return QModelIndex()

childItem = index.internalPointer()
if not childItem:
  return QModelIndex()

parentItem = childItem.parent()

if parentItem == self.rootItem:
  return QModelIndex()

return self.createIndex(parentItem.row(), 0, parentItem) # == ERROR ==

TreeView = QTreeView()
TreeModel = NodeTree(TreeView, [['A', ['B', 1]], ['C', 'D'], ['E', 'F']])
TreeView.setModel(TreeModel)
TreeView.show()
```

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Subclassing QAbstractItemModel - struggling with
createIndex()/internalPointer()

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