[PyQt] Multiple inheritance from custom widgets and uic

[Alexander Bruy]

Hi all,

usually I use following code to create a form from the Qt Designer's .ui
file dynamically

from PyQt5 import uic
FORM_CLASS, BASE_CLASS = uic.loadUiType('/path/to/ui/file.ui')

class MyDialog(BASE_CLASS, FORM_CLASS):
    def __init__(self, parent=None):
        super(MyDialog, self).__init__(parent)
        self.setupUi(self)

and everything works fine.

But seems this approach seems does not work with multiple inheritance.
There is a custom dialog class (QDialog subclass with custom UI and some
logic) available in the API library. I want to subclass this custom dialog
and also apply my own UI to it. I tried following code

from PyQt5 import uic
from api.ui import CustomDialogBase

FORM_CLASS, BASE_CLASS = uic.loadUiType('/path/to/ui/file.ui')

class MyDialog(BASE_CLASS, CustomDialogBase, FORM_CLASS):
    def __init__(self, parent=None):
        super(MyDialog, self).__init__(parent)
        self.setupUi(self)

But this raises type error

TypeError: Cannot create a consistent method resolution order (MRO)
for bases QDialog, QgsOptionsDialogBase, Ui_OptionsDialog

As I understand, this is because all classes have the same base class QDialog.

Also I tried to specify only one parent class — custom dialog, as it is
already subclassed from QDialog

from PyQt5 import uic
from api.ui import CustomDialogBase

FORM_CLASS, BASE_CLASS = uic.loadUiType('/path/to/ui/file.ui')

class MyDialog(CustomDialogBase, FORM_CLASS):
    def __init__(self, parent=None):
        super(MyDialog, self).__init__(parent)
        self.setupUi(self)

But this also does not work, with the error

AttributeError: 'MyDialog' object has no attribute 'groupBox'

As I understand, in this case issue is that FORM_CLASS is a QDialog subclass,
not CustomDialogBase's subclass. After some searching I have found this
thread
https://riverbankcomputing.com/pipermail/pyqt/2017-October/039647.html.
Am I right that currently the only way to solve my issue is to construct
form from the compiled .ui file?

Thanks

-- 
Alexander Bruy