Admin StackedPolymorphicInline: how to get instance value from inline child form?

[drivelous]

This might be more django admin specific but figured I should add here. Hi there,

I need to conditionally render a form field field2 depending on the value of another field field1

# models.py
class Rule(models.Model):
    pass

class Action(PolymorphicModel):
    rule = models.ForeignKey(Rule)

class SpecificAction(Action):
    field1 = Boolean
    field2 = CharField

Usually, I'll do conditional rendering of a fields in the get_fields method and check the values of obj -- in example see HELP

# admin.py

class ActionInline(StackedPolymorphicInline):
    class SpecificActionInline(StackedPolymorphicInline.Child):
        model = SpecificActionInline

        def get_fields(self, request, obj=None):
             fields = super(ActionInline.SpecificActionInline, self).get_fields(request, obj)

             # HELP: this doesn't work because obj here refers to the `Rule` instance not `SpecificAction` instance
             if obj.field1 is False:
                 fields.remove('field2')
             return fields

         model = Action
         child_inlines = (SpecificActionInline,)


class RuleAdmin(PolymorphicInlineSupportMixin, admin.ModelAdmin):
    form = RuleForm
    inlines = (ActionInline,)

How would I get the SpecificAction instance in get_fields instead of the Rule instance?

Thank you in advance

[bckohan]

@drivelous The correct place to do this is in the form which will render for each action on a given rule object:

class SpecificActionForm(forms.ModelForm):
    class Meta:
        model = SpecificAction
        fields = "__all__"

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)

        if self.instance and self.instance.pk:
            # hide the field, don't remove it
            if not self.instance.field1:
                field2 = self.fields.get("field2")
                if field2:
                    field2.widget = forms.HiddenInput()
                    field2.required = False

class ActionInline(StackedPolymorphicInline):
    class SpecificActionInline(StackedPolymorphicInline.Child):
        model = SpecificAction
        form = SpecificActionForm  # use your custom form!

    model = Action
    child_inlines = (SpecificActionInline,)