InlineFormSet validation

[César García Tapia]

Hi. I already asked this question in StackOverflow, but I didn't get any useful answer. Let's try here :-)

I have a BaseInlineFormSet, and I'd like to validate a field in the parent form based on the values on the fields of the children. As seen in the docs, the only method to make a custom validation is clean(), but I can't find a way to add errors to the parent form, only for the children.

In the following code I build a formula. Each variable comes from a inner form, and if the global formula don't validate, I'd like to add an error to the parent's form field formula

class CustomInlineFormSet(BaseInlineFormSet):

    def clean(self):

        formula = self.instance.formula

        variables = []

        for form in self.forms:

            if 'formula_variable' in form.cleaned_data:

                variables.append(form.cleaned_data['formula_variable'])

        valid, msg = validate_formula(formula, variables)

        if not valid:

            WHAT HERE???

Thank you!!

[Russell Keith-Magee]

Hi Cesar,

It's all the documentation:

https://docs.djangoproject.com/en/dev/topics/forms/formsets/#custom-formset-validation

You just have to raise a ValidationError(); Django will then add an error that spans the entire formset. 

If you want to evaluate errors in clean(), but force the actual error to appear against a specific field, that's possible too - you just need to emulate what Django is doing behind the scenes. That means inserting the error into the error dictionary, and removing the error value from cleaned_data:

    self._errors['field name'] = self.error_class(['This field has a problems'])

    del cleaned_data['field_name']

You might need to do this if you won't know if a specific value is valid until you've checked all the individual values (e.g., A must be greater than B - you can't check that until you know both A and B exist, which won't be the case in the clean_A and clean_B methods)

I hope that helps!

Yours,

Russ Magee %-)

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[César García Tapia]

Hi, Russell, thanks for answering :-)

Your answer helps me, but not completely. I can add the error with this:

    self._errors.append({'formula': self.error_class([msg])})  # self._errors in a BaseInlineFormSet is a list of dictionaries, not a dictionary, like you say.

But I don't know how to reach the cleaned_data of the parent form. If I do this:

    del self.cleaned_data['formula']

It says that the parent form doesn't have a 'cleaned_data' attribute.

So I can make the InlineFormSet validation fail, but I can't show the error in my template.

Any suggestion?

Thank you!!

[César García Tapia]

Ok, thanks to Russell's help in IRC I managed to solve this. Thank you so much!!