How do you make django form validation dynamic?

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 开发者_如何学编程only raises an error if both of the fields above are invalid but excepts one being invalid so long as the other is valid?

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

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          

Here's my solution which really works... (tested)

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

    if self.data and self.data.get('field_name') != 'SOMETHING':
        self.fields.get('field_name2').required = True

This makes field_name2 a required field if field_name's input was not 'SOMETHING'. Django rocks!

You should take a look at this package django-extra-field-validation

from django.db import models
from extra_validator import FieldValidationMixin


class MyModel(FieldValidationMixin, models.Model):
    uploadedfile = models.FileField(upload_to='upload/path', blank=True, default='')
    url_address = models.URLField(blank=True, default='') 
    
    REQUIRED_TOGGLE_FIELDS = ['uploadedfile', 'url_address']

This will validate that only one of the fields can be provided raising validation error if both are used.