def setEditorData(self, editor, index):
        if not editor:
            return

        column = index.column()
        value = index.model().data(index, Qt.EditRole)

        fieldType = FieldsMappingModel.columns[column]['type']
        if fieldType == QVariant.Type:
            editor.setCurrentIndex(editor.findData(value))

        elif fieldType == QgsExpression:
            editor.setField(value)

        else:
            QStyledItemDelegate.setEditorData(self, editor, index)

    def setModelData(self, editor, model, index):
        if not editor:
            return

        column = index.column()

        fieldType = FieldsMappingModel.columns[column]['type']
        if fieldType == QVariant.Type:
            value = editor.itemData(editor.currentIndex())
            if value is None:
                value = QVariant.Invalid
            model.setData(index, value)

        elif fieldType == QgsExpression:
            (value, isExpression, isValid) = editor.currentField()
            model.setData(index, value)

        else:
            QStyledItemDelegate.setModelData(self, editor, model, index)

    def createEditor(self, parent, option, index):
        column = index.column()

        fieldType = FieldsMappingModel.columns[column]['type']
        if fieldType == QVariant.Type:
            editor = QComboBox(parent)
            for key, text in FieldsMappingModel.fieldTypes.iteritems():
                editor.addItem(text, key)

        elif fieldType == QgsExpression:
            editor = QgsFieldExpressionWidget(parent)
            editor.setLayer(index.model().layer())
            editor.fieldChanged.connect(self.on_expression_fieldChange)

        else:
            editor = QStyledItemDelegate.createEditor(self, parent, option, index)

        editor.setAutoFillBackground(True)
        return editor

 def eventFilter(self, editor, event):
     if event.type() == QEvent.FocusOut and hasattr(editor, 'canFocusOut'):
         if not editor.canFocusOut:
             return False
     return QStyledItemDelegate.eventFilter(self, editor, event)

 def __init__(self, parent=None):
     QStyledItemDelegate.__init__(self, parent)