kopia lustrzana https://github.com/rtts/django-simplecms
45 wiersze
1.5 KiB
Python
45 wiersze
1.5 KiB
Python
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from django.db import models
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class NumberedModel(models.Model):
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def number_with_respect_to(self):
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return self.__class__.objects.all()
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def _renumber(self):
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'''Renumbers the queryset while preserving the instance's number'''
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queryset = self.number_with_respect_to()
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field_name = self.__class__._meta.ordering[-1].lstrip('-')
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this_nr = getattr(self, field_name)
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if this_nr is None:
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this_nr = len(queryset) + 1
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# The algorithm: loop over the queryset and set each object's
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# number to the counter. When an object's number equals the
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# number of this instance, set this instance's number to the
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# counter, increment the counter by 1, and finish the loop
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counter = 1
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inserted = False
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for other in queryset.exclude(pk=self.pk):
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other_nr = getattr(other, field_name)
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if counter >= this_nr and not inserted:
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setattr(self, field_name, counter)
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inserted = True
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counter += 1
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if other_nr != counter:
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setattr(other, field_name, counter)
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super(NumberedModel, other).save()
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counter += 1
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if not inserted:
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setattr(self, field_name, counter)
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def save(self, *args, **kwargs):
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self._renumber()
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super(NumberedModel, self).save(*args, **kwargs)
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def delete(self, *args, **kwargs):
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super(NumberedModel, self).delete(*args, **kwargs)
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self._renumber()
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class Meta:
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abstract = True
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