How do I set item delegates for multiple columns in a model that is processed by a proxy model?

Question

I set my item delegates like so:

COMBOBOX_ITEMS_FRUITS = ['Apple', 'Banana']
COMBOBOX_ITEMS_COLORS = ['Red', 'Green', 'Blue']

self.treeview.setItemDelegateForColumn(COLUMN_A, ComboBoxDelegate(COMBOBOX_ITEMS_FRUITS))
self.treeview.setItemDelegateForColumn(COLUMN_B, ComboBoxDelegate(COMBOBOX_ITEMS_COLORS))

After the model is set as the source model for the proxy model, my app crashes but no errors were thrown:

self.model_source = treeview_model
self.sf_proxy_model.setSourceModel(self.model_source)

It seems that I can only use one setItemDelegateForColumn when a sortfilterproxymodel is used to process the source model.

ComboBoxDelegate is defined as follows:

class ComboBoxDelegate(QStyledItemDelegate):
    def __init__(self, items):
        super(ComboBoxDelegate, self).__init__()

        self.items = items

    def createEditor(self, parent, option, index):
        editor = QComboBox(parent)
        editor.setAutoFillBackground(True)

        for item in self.items:
            editor.addItem(item)

        return editor

    def setEditorData(self, editor, index):
        current_index = editor.findText(index.model().data(index), Qt.MatchExactly)
        editor.setCurrentIndex(current_index)

    def setModelData(self, editor, model, index):
        item_index = model.mapToSource(index)
        item = model.sourceModel().item(item_index.row(), 0)

        if index.parent().row() == -1 and item.hasChildren():
            for row in range(item.rowCount()):
                child = item.child(row, 3)
                child.setText(editor.currentText())

        model.setData(index, editor.currentText())

    def updateEditorGeometry(self, editor, option, index):
        editor.setGeometry(option.rect)

Answer 1

The treeview does not take ownership of the delegate, so you must keep a reference to it yourself (otherwise it will be garbage-collected by python):

    self.delegate1 = ComboBoxDelegate(COMBOBOX_ITEMS_FRUITS)
    self.delegate2 = ComboBoxDelegate(COMBOBOX_ITEMS_COLORS)
    self.view.setItemDelegateForColumn(COLUMN_A, self.delegate1)
    self.view.setItemDelegateForColumn(COLUMN_B, self.delegate2)