form.py 文件源码

def formfield_for_manytomany(self, db_field, **kwargs):
        """
        Get a form Field for a ManyToManyField.
        """
        # If it uses an intermediary model that isn't auto created, don't show
        # a field in admin.

        if not db_field.remote_field.through._meta.auto_created:
            return None
        db = kwargs.get('using')

        if 'queryset' not in kwargs:
            queryset = self.get_field_queryset(db, db_field)
            if queryset is not None:
                kwargs['queryset'] = queryset

        form_field = db_field.formfield(**kwargs)
        if isinstance(form_field.widget, SelectMultiple) and not isinstance(form_field.widget, CheckboxSelectMultiple):
            msg = _('Hold down "Control", or "Command" on a Mac, to select more than one.')
            help_text = form_field.help_text
            form_field.help_text = string_concat(help_text, ' ', msg) if help_text else msg
        return form_field