Re: Builder derived widgets with properties -- error validate_and_install_class_property: assertion 'class->set_property != NULL' failed

[Kjell Ahlstedt <kjellahlstedt gmail com>]

Den 2022-08-29 kl. 23:37, skrev Dan Lo Forte:
> I have a glade file from which I load a derived widget that has a 
> Glib::Property.  When I load the main window, I get the following error:
>
> ```
>
> GLib-GObject-CRITICAL **: validate_and_install_class_property: 
> assertion 'class->set_property != NULL' failed
>
> ```
>
> I have created a simplified example, as per this page: 
> https://developer-old.gnome.org/gtkmm-tutorial/stable/sec-builder-using-derived-widgets.html.en, 
> using a derived Gtk::Button and still see the error.
Your simplified example is very similar to the example at 
https://gitlab.gnome.org/GNOME/gtkmm-documentation/-/tree/gtkmm-3-24/examples/book/builder/derived, 
which does not print an error message. There is a significant difference 
in the glade file (glade_str). You shall change GtkButton to 
gtkmm__CustomObject_DerivedButtonProp, the Gtype name of your button class.