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On 03/10/2013 04:19 PM, Joshua Immanuel wrote:
> My application is based on Grok. Whenver, I change a method-name or
> add a method to a Model, Grok fails to load the previous version from
> the ZODB. I resorted to writing simple generations (zope.generations)
> to update the stored model objects.
>
> For 'method name' changes, this basically means: 1. create new object
> 2. copy every single attribute of old-object to the new-object 3.
> delete old-object 4. save new-object
>
> How does everyone else do this? Or is there a way to make
> grok/zope/zodb not persist the method-names and signatures in a
> content component (grok Model)?
Method names are not stored in the ZODB at all: only the instance
attributes are stored.
What you report doesn't correspond with how ZODB is designed, nor with
how Zope has been using it forever. For instance, I can create a class
inside a module:, derived from Persistent:
# foo.py, v1
from persistent import Persistent
class Foo(Persistent):
def __init__(self, bar, baz):
self.bar = bar
self.baz = baz
and make instances of it, adding them to another persistent object:
from ZODB.DB import DB
from ZODB.FileStorage import FileStorage
db = DB(FileStorage('/tmp/data.fs'))
conn = db.open()
root = db.root()
from foo import Foo
root.foo = Foo('bar 1', 0)
import transaction
transation.commit()
and then later modify 'foo.py', adding methods to the Foo class
# foo.py, v2
from persistent import Persistent
class Foo(Persistent)
def __init__(self, bar, baz):
self.bar = bar
self.baz = baz
def spam(self):
return self.bar * self.baz
and still load the previously created object from the database::
from ZDOB.DB import DB
from ZODB.FileStorage import FileStorage
db = DB(FileStorage('/tmp/data.fs'))
conn = db.open()
root = db.root()
from foo import Foo
assert isinstance(root.foo, Foo)
print root.foo.spam()
If that isn't working for your models, you must be doing something very
weird. Possible issues:
- - Do your model classes derive from Persistent?
- - Do they have attributes with multable values (e.g., native Python dict
or list)? If so, does your code mutate those values without telling the
containing object it has changed?
- - Are you remembering to commit the transaction?
Tres.
- --
===================================================================
Tres Seaver +1 540-429-0999 tsea...@palladion.com
Palladion Software "Excellence by Design" http://palladion.com
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