How do you make django form validation dynamic?

Question

I have a form that needs to have either a valid url or a valid file for uploading:

class ResourceUpload(ModelForm):
   ...        
   uploadedfile = forms.FileField('file')
   url_address = forms.URLField('url') 
   ...

How can I override the FileField and URLField validators so that Django only raises an error if both of the fields above are invalid but excepts one being invalid so long as the other is valid?

Answer 1

my solution
pros: it keeps the asterisk for the really required field and default error messages

class Form(forms.ModelForm):
    field1 = SelectField
    field2 = ...
    field3 = ...

    def __init__(self, *args, **kwargs):
        super(Form, self).__init__(*args, **kwargs)
        if kwargs['data']:
            if kwargs['data'].get('field1') == '1':
                self.fields['field2'].required = True
                self.fields['field3'].required = False
            elif kwargs['data'].get('field1') == '2':
                self.fields['field2'].required = False
                self.fields['field3'].required = True

Answer 2

You'll need to set them both as required=False, so the database backend doesn't need them both filled in, and then use form cleaning:

import forms

class ResourceUpload(ModelForm):
   ...        
   uploadedfile = forms.FileField(required = False, upload_to='put/files/here')
   url_address = forms.URLField(required = False) 
   ...

   def clean(self):
       cleaned_data = self.cleaned_data
       uploadedfile = cleaned_data.get("uploadedfile ")
       url_address = cleaned_data.get("url_address ")

       if not uploadedfile and not url_address :
           raise forms.ValidationError("Provide a valid file or a valid URL.")
       
       return cleaned_data