finsprings

class FooAdminForm(forms.ModelForm):
    json_serializer = serializers.get_serializer("json")()

    # TODO: make it hide the colon before our empty label
    # TODO: figure out how not to break encapsulation to set the value
    orig_model_json = forms.CharField(widget=forms.HiddenInput, label="")


    def __init__(self, data=None, files=None, auto_id='id_%s', prefix=None,
                 initial=None, error_class=ErrorList, label_suffix=':',
                 empty_permitted=False, instance=None):
        super(CaseAdminForm, self).__init__(data, files, auto_id, prefix, initial,
                                         error_class, label_suffix, empty_permitted, instance)
        if instance:
            omj = self.fields["orig_model_json"]
            omj.initial = self.json_serializer.serialize((instance,), ensure_ascii=False)

    class Meta:
        model = Foo

    def clean(self):
        omj = self.fields["orig_model_json"]
        print "omj:",omj.initial
        if omj.initial:
            current_model_json = self.json_serializer.serialize((self.instance,), ensure_ascii=False)
            if current_model_json != omj.initial:
                raise forms.ValidationError("Record has changed since you started editing it.")

        return self.cleaned_data