Within the model "Example" I have two fields:
-"description" (varchar, length 64). -"description_length" integer. description_length has different value for each record, and it is always between 1 and 64.
In a Django form how is possible set the maxlength description equal to the description_length variable value?
Sure thing.
class ExampleForm(forms.ModelForm): class Meta: model = Example def __init__(self, *args, **kwargs): super(ExampleForm, self).__init__(*args, **kwargs) if self.instance: self.fields['description'].max_length = self.instance.description_length Just be sure your description model field is big enough to accomodate the text of description_length:
class Example(models.Model): MAX_DESCRIPTION_LENGTH = 1024 description = models.CharField(max_length=MAX_DESCRIPTION_LENGTH) description_length = models.IntegerField( validators=MaxValueValidator(MAX_DESCRIPTION_LENGTH)) 