Hi Simon,
thank you very much for your help. I wasn't aware of the possibility of
callable class instances. This solved my problem entirely.
Regards,
Jann
On Tuesday, November 25, 2014 10:07:57 PM UTC+1, Simon Charette wrote:
>
> Hi Jann,
>
> I think you'll need to write a custom deletion handler for this.
>
> The following should work:
>
> from django.db import models
>
>
> class SetNull(object):
> """Deletion handler that behaves like `SET_NULL` but also
> takes a list of extra fields to NULLify."""
>
> def __init__(self, *fields):
> self.fields = fields
>
> def __call__(self, collector, field, sub_objs, using):
> # Set the field this is attached to NULL
> models.SET_NULL(collector, field, sub_objs, using)
> for field in self.fields:
> models.SET_NULL(collector, field, sub_objs, using)
>
>
> class MyModel(models.Model):
> a = models.CharField(max_length=255, null=True, blank=True)
> b = models.ForeignKey(
> 'MyOtherModel', null=True, blank=True, on_delete=SetNull(a)
> )
>
> Simon
>
>
> Le mardi 25 novembre 2014 12:19:48 UTC-5, Yan a écrit :
>>
>> Dear Django Users,
>>
>> I have been running into a problem with the app I am developing and I
>> haven't been able to find a good solution. Suppose I have the following
>> model:
>>
>> class MyModel(models.Model):
>> a = models.CharField(max_length=255, null=True, blank=True)
>> b = models.ForeignKey('MyOtherModel', null=True, blank=True,
>> on_delete=models.SET_NULL)
>> # some more model fields
>>
>> The task I am trying to accomplish is the following: If an instance of
>> "MyOtherModel" is deleted, a and b of the related MyModel-instance
>> should be set to NULL in the database, but the instance of MyModel with
>> the other fields should remain. The model above only sets b to NULL but
>> not a.
>>
>> Any ideas?
>>
>> Regards,
>>
>> Jann
>>
>>
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