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"""
We perform uniqueness checks explicitly on the serializer class, rather
the using Django's `.full_clean()`.
This gives us better seperation of concerns, allows us to use single-step
object creation, and makes it possible to switch between using the implicit
`ModelSerializer` class and an equivelent explicit `Serializer` class.
"""
from django.core.exceptions import ValidationError
from django.utils.translation import ugettext_lazy as _
from rest_framework.utils.representation import smart_repr
class UniqueValidator:
# Validators with `requires_context` will have the field instance
# passed to them when the field is instantiated.
requires_context = True
message = _('This field must be unique.')
def __init__(self, queryset):
self.queryset = queryset
self.serializer_field = None
def __call__(self, value):
field = self.serializer_field
# Determine the model field name that the serializer field corresponds to.
field_name = field.source_attrs[0] if field.source_attrs else field.field_name
# Determine the existing instance, if this is an update operation.
instance = getattr(field.parent, 'instance', None)
# Ensure uniqueness.
filter_kwargs = {field_name: value}
queryset = self.queryset.filter(**filter_kwargs)
if instance:
queryset = queryset.exclude(pk=instance.pk)
if queryset.exists():
raise ValidationError(self.message)
def __repr__(self):
return '<%s(queryset=%s)>' % (
self.__class__.__name__,
smart_repr(self.queryset)
)
class UniqueTogetherValidator:
requires_context = True
message = _('The fields {field_names} must make a unique set.')
def __init__(self, queryset, fields):
self.queryset = queryset
self.fields = fields
self.serializer_field = None
def __call__(self, value):
serializer = self.serializer_field
# Determine the existing instance, if this is an update operation.
instance = getattr(serializer, 'instance', None)
# Ensure uniqueness.
filter_kwargs = dict([
(field_name, value[field_name]) for field_name in self.fields
])
queryset = self.queryset.filter(**filter_kwargs)
if instance:
queryset = queryset.exclude(pk=instance.pk)
if queryset.exists():
field_names = ', '.join(self.fields)
raise ValidationError(self.message.format(field_names=field_names))
def __repr__(self):
return '<%s(queryset=%s, fields=%s)>' % (
self.__class__.__name__,
smart_repr(self.queryset),
smart_repr(self.fields)
)
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