How to fill model field value from a different ModelForm field with some calculation?

Question

I want to have age field in my ModelForm and use it to fill birth_year in the model.
What is the idiomatic way to do this? What method should I provide in my form or model or meta class?

That depends if you want to fill the `birth_year` field when saving/updating the instance of the model, or do you want it to be a dynamic solution, that wouldn't require saving to update the `birth_year` based on `age`? — WTK, Sep 19 '11 at 08:27

score 3 · Accepted Answer · answered Sep 19 '11 at 09:43

from datetime import datetime
import forms
from myapp.models import MyModel


class MyAgeForm(forms.ModelForm):
    age = forms.IntegerField()
    # define other custom fields here

    class Meta:
       model = MyModel
       # probably define what fields from the model to include/exclude here


    def save(self, *args, **kwargs):
        self.instance.birth_year = datetime.now().year - self.cleaned_data['age']
        return super(MyAgeForm, self).save(*args, **kwargs)

How to fill model field value from a different ModelForm field with some calculation?

1 Answers1