Django Model with math

Asked Nov 23 '15 at 19:39

Active Nov 23 '15 at 19:39

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Hey i have a problem with my django model.

i have one class like this:

class Test(model.Models):
    EV_Nr = models.IntegerField(unique=True)
    Factor = models.DecimalField(max_digits=5, decimal_places=2, blank=False)

class Polter(models.Model):
    EV = models.ForeignKey(Test)
    RM = models.DecimalField(max_digits=10, decimal_places=2, default=0)
    FM = models.DecimalField(max_digits=10, decimal_places=2, default=0)

My Problem:

RM or FM has to be 0, if both >0, it's an error and can not be saved.
but for example: RM = 10 and FM = 0. It's ok. -> and the model has to check for the Factor in my Test Model and to do the following: FM = RM / Faktor(from Test Model) and save it in my databese.

How can i do this. After two days of searching I have no idea.

Thanks for your help

asked Nov 23 '15 at 19:39

Chris R-n

Seen https://docs.djangoproject.com/en/dev/ref/signals/#pre-save ? – Paul Collingwood Nov 23 '15 at 19:45
yes, don't understand everything – Chris R-n Nov 23 '15 at 19:53
well, one way to go is to check the values by pulling the relevant models and then saving if all is ok. http://stackoverflow.com/questions/17645801/when-to-use-pre-save-save-post-save-in-django – Paul Collingwood Nov 23 '15 at 20:08

Django Model with math

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