Override min_value and max_value in IntegerField Django

Question

class A:
  min_v = 1
  max_v = 15
  number1 = IntegerField(min_value=min_v, max_value=max_v)

class B(A):
   number2 = IntegerField(min_value=A.min_v, max_value=A.max_v)

class C(B):
  min_v = 2
  max_v = 20

How to make both number1 and number2 to be in range from 2 to 20 in class C?

I'm thinking about two ways:

In __init__ redeclare self.fields['number1'] like IntegerField(min_value=self.min_v)
Set self.fields['number1'].min_value=self.min_v in __init__ and override setattr() to add validator.

What is the best and the cleanest way?

willeM_ Van Onsem · Accepted Answer · 2021-11-28 19:15:53Z

1

It might be better to add these bounds as validators to the the bounds in the __init__ method of class A and class B. This will make these transparent to C and furthermore C can for example define another IntegerField for that name and thus specify a different widget for that:

from django.core import validators

class A:
    number1 = IntegerField()
    
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        number1 = self.fields['number1']
        number1.validators.append(validators.MinValueValidator(self.min_v))
        number1.validators.append(validators.MaxValueValidator(self.max_v))
        number1.widget.attrs['min'] = number1.min_value = self.min_v
        number1.widget.attrs['max'] = number1.max_value = self.max_v

class B(A):
    number2 = IntegerField()
    
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        number2 = self.field['number2']
        number2.validators.append(validators.MinValueValidator(self.min_v))
        number2.validators.append(validators.MaxValueValidator(self.max_v))
        number2.widget.attrs['min'] = number2.min_value = self.min_v
        number1.widget.attrs['max'] = number2.max_value = self.max_v

edited Nov 28, 2021 at 19:15

answered Nov 28, 2021 at 16:20

willeM_ Van Onsem

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3 Comments

Paul R Over a year ago

I thought about it, but it is not passed to widget attrs.

willeM_ Van Onsem Over a year ago

@AndrewFount: that why you need to append the validators: Django only looks at this when you construct a form field. This thus means that if you later set the .min_value and .max_value, it will not validate properly at the backend side. The .min_value and .max_value are necessary for the bounds at the frontend, since these will be used for a <input type="number" min="..." max="...">.

Paul R Over a year ago

I mean, that widget attrs also should be added: number2.widget.attrs.update({'min': self.min_v, 'max': self.max_v})

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