Persistent

This package provides a base class for persistent objects with the advantage that the object is only marked as changed if an attribute has really changed.

>>> import transaction
>>> from ZODB.tests.util import DB

>>> from lovely import persistent

>>> p = LovelyPersistent()
>>> p._p_changed
False

>>> p.a = 1
>>> db = DB()
>>> conn = db.open()
>>> conn.root()['p'] = p
>>> transaction.commit()

After commiting the changes the object is no longer in changed state.

>>> p._p_changed
False

Setting a with its existing value doesn’t put the object in cahnged state.

>>> p.a
1
>>> p.a = 1
>>> p._p_changed
False

But modifying a :

>>> p.a = 2
>>> p._p_changed
True
>>> transaction.commit()

>>> p._p_changed
False

Deleting an attribute also put the object into changed state.

>>> del p.a
>>> p._p_changed
True

Special Properties

Special property implementations do work too. To show this we use the fieldproperties from zope.schema.

>>> from zope.schema.fieldproperty import FieldProperty
>>> from zope import schema, interface
>>> class IMyFace(interface.Interface):
...     eyesOpen = schema.Bool(default=True, required=False)

>>> class MyFace(persistent.Persistent):
...     eyesOpen = FieldProperty(IMyFace['eyesOpen'])

>>> persistent.tests.MyFace = MyFace
>>> MyFace.__module__ = persistent.tests.setUp.__module__
>>> myFace = conn.root()['myFace'] = MyFace()
>>> transaction.commit()

Default values.

>>> myFace.eyesOpen
True

Validation.

>>> myFace.eyesOpen = 'not always'
Traceback (most recent call last):
...
WrongType: ('not always', <type 'bool'>)

Note, setting to default value does not change the object.

>>> transaction.commit()
>>> myFace.eyesOpen = True
>>> myFace._p_changed
False

>>> transaction.commit()
>>> myFace.eyesOpen = False
>>> myFace._p_changed
True

Changes in lovely.persistent

2007/12/10 0.1.1

moved to zope.org

2007/06/19 0.1.0a1

added zodb to dependencies
added support for fieldproperties

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