Transactional variables are data slots which can store arbitrary values during a
transaction. Transactional variables are guaranteed to vanish when a transaction
finishes or aborts, and specific to a single thread and a single transaction.
They are never shared by different threads.
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Transactional variables are different from user-defined data in a REQUEST object,
in the sense that one request may execute multiple transactions, but not vice
versa. If data should persist beyond a transaction, but must not persist over
a single request, you should use a REQUEST object instead of transactional
Also, transactional variables are different from volatile attributes, because
transactional variables may not disappear within a transaction.
The constraint is that each key must be hashable, so that it can be used as a key to a dictionary.
from Products.ERP5Type.TransactionalVariable import getTransactionalVariable
tv = getTransactionalVariable()
toto = tv['toto']
toto = tv['toto'] = getToto()
The following example shows how to name a transactional variable in order to prevent name conflicts:
acquisition_key = ('_getDefaultAcquiredProperty', self.getPath(), key, base_category,
portal_type, copy_value, mask_value, sync_value,
accessor_id, depends, storage_id, alt_accessor_id, is_list_type, is_tales_type)
The general form to name transactional variables for ERP5 document methods is:
key = (<>, self.getPath(), arg1, arg2, arg3, etc.)
and if the transactional variable not used on an ERP5 document method:
key = (<>, arg1, arg2, arg3, etc.)