Using own field to define others in Django Models

Question

If I want to set a default value in a field and that value is derived from another field from same model. How can do something like that:

class MyModel(models.Model):
     field_1 = models.CharField()
     field_2 = models.Charfield(defualt=field_1 + 'extra info')

karthikr · Accepted Answer · 2015-01-28 20:19:21Z

3

You cannot use the default in this case. You can use the model's save method for this purpose:

class MyModel(models.Model):
    field_1 = models.CharField(max_length=80)
    field_2 = models.Charfield(max_length=80)

    def save(self, *args, **kwargs):
        #Here you can have all kinds of validations you would need

        self.field_2 = self.field_1 + "extra info"
        super(MyModel, self).save(*args, **kwargs)

Now, you can hide/exclude the field_2 from the forms/modelforms if you choose to.

answered Jan 28, 2015 at 20:19

karthikr

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