[PyQt] QAbstractItemModel doesn't require to subclass data method

[Phil Thompson]

On Wed, 8 Oct 2008 22:58:05 +0200, "Filip Gruszczyński"
<gruszczy at gmail.com> wrote:
> When I run following code (of course with some implementation of tree
> objects):
> 
> class QCategorizedItemModel(QAbstractItemModel):
> 
> 	def __init__(self, tree):
> 		QAbstractItemModel.__init__(self)
> 		self.__root = tree
> 
> 	def root(self):
> 		return self.__root
> 
> 	def columnCount(self, parent):
> 		# there is only one column with all categories inside
> 		return 1
> 
> 	def rowCount(self, parent):
> 		return parent.internalPointer().childrenCount()
> 
> 	def flags(self, index):
> 		if not index.isValid():
> 			return 0
> 		return Qt.ItemIsSelectable
> 
> 	def index(self, row, column, parent):
> 		if column != 0:
> 			return QModelIndex()
> 		child = parent.internalPointer().child(row)
> 		if child:
> 			return self.createIndex(row, column, child)
> 		else:
> 			return QModelIndex()
> 
> 	def parent(self, index):
> 		internal = index.internalPointer()
> 		if internal == self.__pointer:
> 			return QModelIndex()
> 		return createIndex(internal.childNumber(), 0, internal)
> 
> it displayed an empty tree view and didn't shout about the need of
> subclassing data method, which is pure virtual. I don't know it that's
> a problem.

Abstract methods only raise an exception if they are actually called. If
your model is empty (eg. if rowCount() returns 0) then this might not
happen.

Phil