How to make a field of a model form read-only when a certain field of an instance is True (Django)?

Question

So lets say I have these classes in my models.py :

class Result(models.Model):
  grade = models.CharField(max_length=10)
  checked = models.BooleanField(blank=False, default=False) 
  checker = models.ForeignKey(User, on_delete=models.CASCADE)

class User(models.Model):
  name = models.CharField(max_length=10)

And lets say i have a model form in my forms.py :

class EnterResult(forms.ModelForm):
    class Meta:
       model = Result
       exclude = ['checked']

I know to pass an instance of a form in views.py you have to:

result = Result.objects.get(pk=pk)
form = EnterResult(instance=result)
return render(request, ...)

Now how do i make checker a read-only input when the instance that is passed has it's field checked = True . I feel like it has something to do with overriding the ___init___(self, *args, **kwargs) .

Answer 1

Yes, overriding __init__ for your form is the thing to do.

def __init__(self, *args, **kwargs):
    super().__init__(*args, **kwargs)
    instance = getattr(self, 'instance', None)
    if instance and instance.checked:
        self.fields["checker"].disabled = True

https://docs.djangoproject.com/en/3.0/ref/forms/fields/#disabled