Re: How to add an element of derived data to a Django model?

I tried Aaron's method. Django validated the model.

However, when I added property "c" to the administration interface's list of fields, It threw an error:

'myModelAdmin.fields' refers to field 'status' that is missing from the form.

Request Method:	GET
Request URL:	http://VVV/admin/
Django Version:	1.4.3
Exception Type:	ImproperlyConfigured
Exception Value:	'myModelAdmin.fields' refers to field 'status' that is missing from the form.
Exception Location:	/usr/lib/python2.6/site-packages/django/contrib/admin/validation.py in check_formfield, line 396
Python Executable:	/usr/bin/python
Python Version:	2.6.8
Python Path:	['/WWW/XXX/YYY/ZZZ', '/usr/lib/python26.zip', '/usr/lib/python2.6', '/usr/lib/python2.6/plat-linux2', '/usr/lib/python2.6/lib-tk', '/usr/lib/python2.6/lib-old', '/usr/lib/python2.6/lib-dynload', '/usr/lib/python2.6/site-packages', '/usr/lib/python2.6/site-packages/setuptools-0.6c11-py2.6.egg-info']
Server time:	Sat, 5 Jan 2013 16:17:42 -0500

On Saturday, January 5, 2013 12:16:30 PM UTC-5, Tundebabzy wrote:

I think you can write a function that returns a > b and then make it a
getter method with python's property.

i would have given an example but typing code from my phone isn't very
appealing.

Sent from my Windows Phone

-----Original Message-----
From: Saqib Ali
Sent: 1/5/2013 5:50 PM
To: django...@googlegroups.com
Subject: How to add an element of derived data to a Django model?




I have a Django Model as follows:





class myModel(models.Model):


 a = models.IntegerField()


 b = models.IntegerField()




I want to add a models.BooleanField() named c to the myModel class.
However the value of c is simply derived from a and b so I don't want
it to be stored in the Database.

I want to c to be True if a > b, otherwise False. I want c to reflect
the correct/current value even when a and b get modifed. And I want to
be able to access c using myModel.c just like I can access a and b.




Is there any way to do this?

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