[Zope-dev] Storing references in objects accross requests - bad or OK?
hello,
I am am worrying a problem here, where I need to store references to
objects in my own objects, while at the same time needing to store and
retreive my objects later.
Here is an example of what I need to do:
in a product BooTool for Zope I have:
class Foo:
def __init__(self, data, ref_a):
self.data = data
self.a_handle = ref_a
self.stuff = []
def bar(self):
# do something with self.stuff
cool = self.a_handle('one')
self.stuff.append(cool)
return self.stuff
def getStuff(data, ref_a):
his method is available to Zope from the tool boo_tool
return Foo(data, ref_a)
in a python script I have a pythonscript:
my_ob = context.boo_tool.getStuff('123', container.my_script)
return my_ob
so my_ob contains a reference to the my_script Pythonscript/ZSQL Method.
What happens if I store my_ob in a session storage for instance and
later retrieve it and do my_ob.bar() ?
What bad things can happen?
Thanks for any input.
/dario
--
-- ---
Dario Lopez-Kästen, IT Systems Services Chalmers University of Tech.
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Re: [Zope-dev] Storing references in objects accross requests - bad or OK?
Dario Lopez-Kästen wrote at 2004-6-13 12:43 +0200: I am am worrying a problem here, where I need to store references to objects in my own objects, while at the same time needing to store and retreive my objects later. Your problem can be summarized by storing acquisition wrappers (of persistent objects) across requests. This is very difficult! You have a very good chance to get burned. You cannot store them in the ZODB as acquisition wrappers cannot be stored there. Currently, the ZODB silently unmantles acquisition wrappers. They may be rebound on access -- but this will not give you the original acquisition context and behaviour can be drastically different. You cannot store them via module global data structures as the values (indirectly) reference persitent objects. You must never put persistent objects outside the scope of its ZODB connection as this will give nasty (non deterministic) persistency bugs. You could store such values as volatile attributes (_v_) of persistent objects. However, volatile attributes are not completely reliable (as the name suggests). And they are (ZODB) connection local -- another connection does not see them. You may put such objects into attributes of the ZODB connection itself. Again, they will be connection local. Urgent recommendation: avoid storing acquisition wrapped objects across requests, store paths instead and locate the objects by means of the paths. -- Dieter ___ Zope-Dev maillist - [EMAIL PROTECTED] http://mail.zope.org/mailman/listinfo/zope-dev ** No cross posts or HTML encoding! ** (Related lists - http://mail.zope.org/mailman/listinfo/zope-announce http://mail.zope.org/mailman/listinfo/zope )
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