How can I implement field validation in Django model forms?

How can I implement field validation in Django model forms?

You can implement field validation in Django model forms by overriding the clean() method or using field-specific validators.

Can you give me an example of using the clean() method?

Sure! In your form class, you can define a clean_<fieldname>() method to validate a specific field. For example:

class MyForm(forms.ModelForm):
    def clean_age(self):
        age = self.cleaned_data.get('age')
        if age < 0:
            raise forms.ValidationError('Age cannot be negative.')
        return age

What if I want to validate multiple fields together?

You can override the clean() method in your form class to validate multiple fields together. Here's an example:

class MyForm(forms.ModelForm):
    def clean(self):
        cleaned_data = super().clean()
        start_date = cleaned_data.get('start_date')
        end_date = cleaned_data.get('end_date')
        if start_date and end_date and start_date > end_date:
            raise forms.ValidationError('Start date must be before end date.')