Viewing file:  mixins.py (1.76 KB) -rw-r--r--
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from django.core import checks
NOT_PROVIDED = object()
class FieldCacheMixin:
"""Provide an API for working with the model's fields value cache."""
def get_cache_name(self):
raise NotImplementedError
def get_cached_value(self, instance, default=NOT_PROVIDED):
cache_name = self.get_cache_name()
try:
return instance._state.fields_cache[cache_name]
except KeyError:
if default is NOT_PROVIDED:
raise
return default
def is_cached(self, instance):
return self.get_cache_name() in instance._state.fields_cache
def set_cached_value(self, instance, value):
instance._state.fields_cache[self.get_cache_name()] = value
def delete_cached_value(self, instance):
del instance._state.fields_cache[self.get_cache_name()]
class CheckFieldDefaultMixin:
_default_hint = ('<valid default>', '<invalid default>')
def _check_default(self):
if self.has_default() and self.default is not None and not callable(self.default):
return [
checks.Warning(
"%s default should be a callable instead of an instance "
"so that it's not shared between all field instances." % (
self.__class__.__name__,
),
hint=(
'Use a callable instead, e.g., use `%s` instead of '
'`%s`.' % self._default_hint
),
obj=self,
id='fields.E010',
)
]
else:
return []
def check(self, **kwargs):
errors = super().check(**kwargs)
errors.extend(self._check_default())
return errors
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