How can I customize error messages in Django ModelForms?

How can I customize error messages in Django ModelForms?

You can customize error messages in Django ModelForms by overriding the error_messages attribute in your form class.

Can you show me an example of how to do that?

Sure! Here's a simple example:

from django import forms

class MyForm(forms.ModelForm):
    class Meta:
        model = MyModel
        fields = ['my_field']
        error_messages = {
            'my_field': {
                'required': 'This field is mandatory!',
                'invalid': 'Enter a valid value!'
            }
        }

What if I want to add custom validation as well?

You can add custom validation by overriding the clean method in your form class. Here's an example:

def clean_my_field(self):
    data = self.cleaned_data['my_field']
    if not some_condition(data):
        raise forms.ValidationError('Custom validation error!')
    return data