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- from django.contrib.messages.storage.base import BaseStorage
- from django.contrib.messages.storage.cookie import CookieStorage
- from django.contrib.messages.storage.session import SessionStorage
- class FallbackStorage(BaseStorage):
- """
- Tries to store all messages in the first backend, storing any unstored
- messages in each subsequent backend backend.
- """
- storage_classes = (CookieStorage, SessionStorage)
- def __init__(self, *args, **kwargs):
- super(FallbackStorage, self).__init__(*args, **kwargs)
- self.storages = [storage_class(*args, **kwargs)
- for storage_class in self.storage_classes]
- self._used_storages = set()
- def _get(self, *args, **kwargs):
- """
- Gets a single list of messages from all storage backends.
- """
- all_messages = []
- for storage in self.storages:
- messages, all_retrieved = storage._get()
- # If the backend hasn't been used, no more retrieval is necessary.
- if messages is None:
- break
- if messages:
- self._used_storages.add(storage)
- all_messages.extend(messages)
- # If this storage class contained all the messages, no further
- # retrieval is necessary
- if all_retrieved:
- break
- return all_messages, all_retrieved
- def _store(self, messages, response, *args, **kwargs):
- """
- Stores the messages, returning any unstored messages after trying all
- backends.
- For each storage backend, any messages not stored are passed on to the
- next backend.
- """
- for storage in self.storages:
- if messages:
- messages = storage._store(messages, response,
- remove_oldest=False)
- # Even if there are no more messages, continue iterating to ensure
- # storages which contained messages are flushed.
- elif storage in self._used_storages:
- storage._store([], response)
- self._used_storages.remove(storage)
- return messages
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