How can I validate a Django ModelForm?

How can I validate a Django ModelForm?

You can validate a Django ModelForm by overriding the clean() method or using field-specific validation methods.

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

Sure! In your ModelForm, you can define a clean() method like this:

class MyForm(forms.ModelForm):
    def clean(self):
        cleaned_data = super().clean()
        field_value = cleaned_data.get('field_name')
        if not field_value:
            raise forms.ValidationError('This field cannot be empty.')
        return cleaned_data

What about field-specific validation?

For field-specific validation, you can define a method named clean_<fieldname>(). For example:

class MyForm(forms.ModelForm):
    def clean_field_name(self):
        value = self.cleaned_data.get('field_name')
        if value < 0:
            raise forms.ValidationError('Value must be positive.')
        return value