Hi all,
it's only now that I came across this interesting discussion.
I tried similar things but what I wanted to protect was my cached
data. And session.merge(obj, dont_load=True) triggers these
AssertionErrors. :-(
So I went for a MapperExtension instead. The after_update method can
still prevent changes from being committed to the database. This
solution is not very elegant, however.
Best regards
Klaus
On 22 Dez. 2007, 17:03, Michael Bayer <[EMAIL PROTECTED]>
wrote:
> On Dec 22, 2007, at 12:34 AM, Andreas Jung wrote:
>
>
>
>
>
> > --On 21. Dezember 2007 16:33:34 -0500 Michael Bayer <[EMAIL PROTECTED]
> > > wrote:
>
> >> On Dec 21, 2007, at 3:13 PM, Rick Morrison wrote:
>
> >> I think the only way something like this should be done is as a test
> >> fixture which decorates classes during unit tests. It would be
> >> fairly clumsy to have in production code.
>
> >> If you have coworkers who write broken code, the way you solve that
> >> is
> >> by having unit tests which will fail when the coworkers in question
> >> do
> >> something theyre not supposed to. If other people are writing code
> >> that sets attrbutes its not supposed to and breaks things, you need
> >> more tests to catch those conditions. If youre putting code into
> >> production that hasnt been tested, then you need a build process,
> >> automated testing, etc. There is definitely a "best practice" here
> >> and test driven development is it.
>
> > With all respect, this is not a useful answer. Even with tests
> > (unittests and weeks of manual tests) I had the case that a simple
> > programming error
> > (of my own) produced a data disaster after some weeks. There is no
> > 100% test coverage. Tests don't solve all problems. There is
> > sometimes the need for a better security belt.
>
> I am certainly suggesting a fixture that detects illegal assignments
> to attributes. That it be limited to just unit tests is only a
> suggestion. To establish this functionality regardless of
> environment, like Rick said just create properties which prohibit
> assignment. Create mappers like this:
>
> class AttrGetter(object):
> def __init__(self, name):
> self.name = name
> def __get__(self, instance, name):
> if instance is None:
> return self
> return getattr(instance, '_' + name)
> def __set__(self, instance, value):
> raise AssertionError("Sets are not allowed")
> def __delete__(self, instance):
> raise AssertionError("Deletes are not allowed")
>
> class MyClass(object):
> somecolumn = AttrGetter('somecolumn')
> someothercolumn = AttrGetter('someothercolumn')
>
> mapper(MyClass, sometable, properties={
> '_somecolumn':sometable.c.somecolumn,
> '_someothercolumn':sometable.c.someothercolumn
>
> })
>
> To automate the above process with no modifications to source code,
> create an instrumented mapper() function which applies the above
> recipe to all table columns:
>
> from sqlalchemy.orm import mapper as _mapper
> def mapper(cls, table, **kwargs):
> attrs = {}
> for c in table.c:
> attrs['_' + c.key] = c
> setattr(cls, c.key, AttrGetter(c.key))
> properties = kwargs.setdefault('properties', {})
> properties.update(attrs)
> return _mapper(cls, table, **kwargs)
>
> Hope this helps.
--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"sqlalchemy" group.
To post to this group, send email to sqlalchemy@googlegroups.com
To unsubscribe from this group, send email to [EMAIL PROTECTED]
For more options, visit this group at
http://groups.google.com/group/sqlalchemy?hl=en
-~----------~----~----~----~------~----~------~--~---
