Django custom validation of multiple fields in a form

Question

for which I want to validate a number of fields in a custom clean method.

I have this so far:

class ProjectInfoForm(forms.Form):
    module = forms.ModelChoiceField(
        queryset=Module.objects.all(),
    )
    piece = forms.CharField(
        widget=forms.Select(),
        required=False,
    )
    span = forms.IntegerField(
        max_value=100,
        initial=48
    )
    max_span = forms.IntegerField(
        max_value=100,
        initial=0
    )


    def clean(self):
        span = self.cleaned_data['span']
        max_span = self.cleaned_data['max_span']
        piece = self.cleaned_data.['piece']

        # validate piece 
        try:
            Piece.objects.get(pk=m)
        except Piece.DoesNotExist:
            raise forms.ValidationError(
                'Illegal Piece selected!'
            )
            self._errors["piece"] = "Please enter a valid model"

        # validate spans
        if span > max_span:
            raise forms.ValidationError(
                'Span must be less than or equal to Maximum Span'
            )
            self._errors["span"] = "Please enter a valid span"
        return self.cleaned_data

However, this only gives me one of the messages if both clauses invalidate. How can I get all the invalid messages. Also I do not get the field-specific messages - how do I include a message to be displayed for the specific field?

Any help much appreciated.

mVChr · Accepted Answer · 2012-12-12 18:05:33Z

8

Store the errors and don't raise them until the end of the method:

def clean(self):
    span = self.cleaned_data['span']
    max_span = self.cleaned_data['max_span']
    piece = self.cleaned_data.['piece']
    error_messages = []

    # validate piece 
    try:
        Piece.objects.get(pk=m)
    except Piece.DoesNotExist:
        error_messages.append('Illegal Piece selected')
        self._errors["piece"] = "Please enter a valid model"

    # validate spans
    if span > max_span:
        error_messages.append('Span must be less than or equal to Maximum Span')
        self._errors["span"] = "Please enter a valid span"

    if len(error_messages):
        raise forms.ValidationError(' & '.join(error_messages))

    return self.cleaned_data

answered Dec 12, 2012 at 18:05

mVChr

50.3k11 gold badges111 silver badges105 bronze badges

Sign up to request clarification or add additional context in comments.

5 Comments

XORcist Over a year ago

Validation concerning only a single field should happen in a clean_FIELDNAME method on the form.

Darwin Tech Over a year ago

This answer works for me - is there something inherently wrong with this approach then?

XORcist Over a year ago

@DarwinTech not really, but the clean method is conceptually meant for form-spanning (multi-field) validation. Single fields should have their own clean_FIELDNAME method.

Darwin Tech Over a year ago

ok. But my instance does validate multi-field does it not? I am validating span and max_span together.

Akshay Over a year ago

Did you mean self.add_error(field_name, message) instead of self._error[field_name]=message? You should also consider the reason for having _ - private variable.

XORcist · Accepted Answer · 2012-12-12 18:11:00Z

1

You should write a custom clean_FIELDNAME method in this case. That way, field centric validation errors can later be displayed as such when using {{form.errors}} in your template. The clean method o.t.h. is for validating logic that spans more than one field. Take a look through the link I posted above, everything you need to know about validating django forms is in there.

edited Dec 12, 2012 at 18:11

answered Dec 12, 2012 at 18:01

XORcist

4,36726 silver badges32 bronze badges

Comments

anacarolinats · Accepted Answer · 2012-12-12 18:07:27Z

0

It happens because you are using raise. Try replace it by these two line in your code:

del self.cleaned_data['piece']

and

del self.cleaned_data['span']

answered Dec 12, 2012 at 18:07

anacarolinats

6678 silver badges19 bronze badges

Comments

user535883 · Accepted Answer · 2019-08-14 19:24:09Z

0

It appears this has changed in later versions of Django (this seems to work in 2.1 and later):


from django import forms

class ContactForm(forms.Form):
    # Everything as before.
    ...

    def clean(self):
        cleaned_data = super().clean()
        cc_myself = cleaned_data.get("cc_myself")
        subject = cleaned_data.get("subject")

        if cc_myself and subject and "help" not in subject:
            msg = "Must put 'help' in subject when cc'ing yourself."
            self.add_error('cc_myself', msg)
            self.add_error('subject', msg)

https://docs.djangoproject.com/en/dev/ref/forms/validation/#raising-multiple-errors has more details.

answered Aug 14, 2019 at 19:24

user535883

Collectives™ on Stack Overflow

Django custom validation of multiple fields in a form

4 Answers 4

5 Comments

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

5 Comments

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related