Django Admin: Making mandatory fields non-mandatory dynamically

Question

How can I make mandatory fields non-mandatory when another [associated] field has a certain value?

Let's assume I have the following models:

class foo(models.Model):
    bar = models.CharField(max_length=200)
    foo_date = models.DateTimeField()

When I save, and bar contains a certain value, i'd like foo_date to become non-mandatory. How do I accomplish that? Thanks.

Answer 1

I think it would just be a matter of setting foo_barr to blank=True, and then implementing your own Form and custom validation for the Admin model to use. See this part of the documentation -- Adding custom validation to admin

Answer 2

T.Stone is right. This is how you do it with a Model Form:

class foo(models.Model):
    bar = models.CharField(max_length=200)
    foo_date = models.DateTimeField()

class ClientAdmin( MyModelAdmin ):
    form = FooModelForm

class FooModelForm( forms.ModelForm ):

    def clean(self):
        cleaned_data = self.cleaned_data
        if cleaned_data.get("bar") == 'some_val' and not cleaned_data.get('foo_date'):
            msg = 'Field Foo Date is mandatory when bar is some_val'
            self._errors[field] = ErrorList([msg])
            del cleaned_data[field]
        return cleaned_data

http://docs.djangoproject.com/en/dev/ref/forms/validation/#cleaning-and-validating-fields-that-depend-on-each-other