48 lines
1.6 KiB
Python
Executable File
48 lines
1.6 KiB
Python
Executable File
from django.contrib.contenttypes.models import ContentType
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from django.db import models
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class Sortable(models.Model):
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"""
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Unfortunately, Django doesn't support using more than one AutoField in a model
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or this class could be simplified.
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`is_sortable` determines whether or not the Model is sortable by determining
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if the last value of `order` is greater than the default of 1, which should be
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present if there is only one object.
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`model_type_id` returns the ContentType.id for the Model that inherits Sortable
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`save` the override of save increments the last/highest value of order by 1
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Override `sortable_by` method to make your model be sortable by a foreign key field.
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Set `sortable_by` to the class specified in the foreign key relationship.
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"""
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order = models.PositiveIntegerField(editable=False, default=1, db_index=True)
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sortable_by = None
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class Meta:
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abstract = True
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ordering = ['order']
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@classmethod
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def is_sortable(cls):
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try:
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max_order = cls.objects.aggregate(models.Max('order'))['order__max']
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except TypeError, IndexError:
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max_order = 0
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return True if max_order > 1 else False
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@classmethod
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def model_type_id(cls):
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return ContentType.objects.get_for_model(cls).id
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def save(self, *args, **kwargs):
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if not self.id:
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try:
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self.order = self.__class__.objects.aggregate(models.Max('order'))['order__max'] + 1
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except TypeError, IndexError:
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pass
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super(Sortable, self).save(*args, **kwargs)
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