Initialize django model capturing a derivative attribute from that moment

Question

I have a model with the following fields:

user = models.ForeignKey(User)
impact = models.IntegerField(default = value)

Where I want value to be User.get_profile().someIntField with User being the same User object that was passed to the first field. How can I do this?

San4ez · Answer 1 · 2012-04-09T10:42:10.077

3

Override save method in your model

class MyModel(models.Model):
    user = models.ForeignKey(User)
    impact = models.IntegerField()

    def save(self, *args, **kwargs):
        if not self.pk:
            self.impact = self.user.get_profile().someIntField
        super(MyModel, self).save(*args, **kwargs)

edited Apr 09 '12 at 10:42

answered Apr 09 '12 at 10:30

San4ez

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but I only want to initialise this value, not reset it every time i save the model object. – Ferguzz Apr 09 '12 at 10:36
is there a parameter i can get to in save() which tells me i'm creating the object? – Ferguzz Apr 09 '12 at 10:36
I updated my answer. If object is created (not updated) impact value will be set. I think it is what you need – San4ez Apr 09 '12 at 10:43

score 2 · Accepted Answer · edited Apr 09 '12 at 14:08

2

def __init__(self, *args, **kwargs):
    super(YourModel, self).__init__(*args, **kwargs)
    self.impact = self.user.get_profile().someIntField

edited Apr 09 '12 at 14:08

Ferguzz

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answered Apr 09 '12 at 10:47

John Mee

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won't this completely break the way the model is initialised? don't you need to call `super(Model, self).__init__(*args, **kwargs)` ? – Ferguzz Apr 09 '12 at 10:52
accepted your answer after a quick read of this http://stackoverflow.com/questions/1355150/django-when-saving-how-can-you-check-if-a-field-has-changed - although I called to super for the init. – Ferguzz Apr 09 '12 at 11:18
cheers, I edited the super in. Feel free to make corrections - i'm not testing it whereas you probably are ;-) – John Mee Apr 09 '12 at 11:23
I'm tempted to edit your question to hold a more relevant subject. Like "Initialize django model capturing a derivative attribute from that moment?" or some such. Can you do that? It's not very search findable as it stands. – John Mee Apr 09 '12 at 11:27
1

Your variant means that you will hit user profile every time you create object. But as I understand Ferguzz need to get default impact value only when saving – San4ez Apr 09 '12 at 11:29

Initialize django model capturing a derivative attribute from that moment

2 Answers2