I have simple find & replace problem with ProxyModel.

My MainTreeModel contains MongoDB documents, witch can contain
DBRefs as fields. (Mongo documents are close relatives of Json objects)

Qt Code: 
  1. ##
  2. #
  3. # One document object in Json format.
  4. # (Just to get the idea of data structure)
  5. #
  6. {
  7.   "_id": {
  8.     "_id": "5273df1f01d418250767b0a3", 
  9.     "__type__": "Base.ObjectId"
  10.   }
  11.   "__type__": "Base.BaseDoc.BaseFlow.Comment", 
  12.   "name": "Topic", 
  13.   "timestamp": {
  14.     "date": 1383332671257, 
  15.     "__type__": "date.datetime"
  16.   }, 
  17.   "author": null, 
  18.   "_ns": "MyProject", 
  19.   "_lock": {
  20.     "__type__": "UUID", 
  21.     "uuid": "e83ad88206bf4e2181d1f848b4708165"
  22.   }, 
  23.   "comments": {
  24.     "__type__": "Base.RefSet"
  25.     "_references": [
  26.          {
  27.         "_type": "Base.BaseDoc.BaseFlow.Comment", 
  28.         "_id": {
  29.           "_id": "527a6b9f01d418250767b135", 
  30.           "__type__": "Base.ObjectId"
  31.         }, 
  32.         "_ns": "MyProject", 
  33.         "_db": null, 
  34.         "_lock": {
  35.           "__type__": "UUID", 
  36.           "uuid": "2470196b220f496590a2adc9645f53b6"
  37.         }, 
  38.         "__type__": "Base.Ref"
  39.       }, 
  40.       {
  41.         "_type": "Base.BaseDoc.BaseFlow.Comment", 
  42.         "_id": {
  43.           "_id": "527a6b2701d418250767b133", 
  44.           "__type__": "Base.ObjectId"
  45.         }, 
  46.         "_ns": "MyProject", 
  47.         "_db": null, 
  48.         "_lock": null, 
  49.         "__type__": "Base.Ref"
  50.       }, 
  51.     ], 
  52.   }, 
  53.   "text": "Comment content text ...", 
  54. }
To copy to clipboard, switch view to plain text mode 

Json is deserialized as document object, which is wrapped
inside Item, and for each field in document a wrapping child Item is created recursively.


deserialization note: dicts that have key='__type__' are deserialized as instances of __type__ keys value.

Now the actual problem.

What I`m trying to archive with QAbstractProxyModel is simple
Ref replacement with the actual document that the Ref is referencing.

But good examples / documentation is bit lacking when it comes to QAbstractProxyModel.
So I turn to you for little help on how to implement this.

Simplified code of my current Proxy. (not working)
Qt Code: 
  1. ##
  2. #
  3. # Proxy model that replaces Ref items
  4. # with the actual referenced tree
  5. #
  6. class DocSolvedRefsProxyModel(QAbstractProxyModel):
  7.     def __init__(self, parent = None):
  8.         super(DocSolvedRefsProxyModel, self).__init__(parent = parent)
  9.         self._mappingTo = dict()
  10.         self._mappingFrom = dict()
  11.  
  12.     def rowCount(self, index=QModelIndex()):
  13.         return self.sourceModel().rowCount(self.mapToSource(index))
  14.  
  15.     def columnCount(self, index=QModelIndex()):
  16.         return self.sourceModel().columnCount(self.mapToSource(index))
  17.  
  18.     def index(self, row, column, parentIndex = QModelIndex()):
  19.         # to be implemented
  20.         return QModelIndex()
  21.  
  22.     def parent(self, childIndex=None):
  23.         if childIndex is None:
  24.             # Trying to get parent widget.
  25.             # Nothing to do with model / view.
  26.             return QObject.parent(self)
  27.  
  28.         # to be implemented
  29.         return QModelIndex()
  30.  
  31.     def mapToSource(self, proxyIndex=QModelIndex()):
  32.         if not proxyIndex.isValid():
  33.             return QModelIndex()
  34.         return self._mappingTo[proxyIndex]
  35.  
  36.     def mapFromSource(self, sourceIndex=QModelIndex()):
  37.         if not sourceIndex.isValid():
  38.             return QModelIndex()
  39.         if sourceIndex in self._mappingFrom:
  40.             return self._mappingFrom[sourceIndex]
  41.         else:
  42.             # checkin for refs & creating mapping
  43.  
  44.             item = sourceIndex.internalPointer()
  45.  
  46.             # Item.obj() method is used to get the actual object contained inside item.
  47.             obj = item.obj()
  48.             if isinstance(obj, Ref):
  49.  
  50.                 proxyIndex = ???
  51.  
  52.        		self._mappingTo[proxyIndex] = sourceIndex
  53. 		self._mappingFrom[sourceIndex] = proxyIndex
To copy to clipboard, switch view to plain text mode 

Little nudge to right direction with the mapFromSource method whould be much appreciated.
/:Aki R.