[Zope-dev] The Application object

[Jeff K. Hoffman]

On Mon, 17 Jul 2000, Shane Hathaway wrote:

> "Jeff K. Hoffman" wrote:
>
> > Do I need to commit or abort even if I don't make changes to the
> > application object? The only thing I need it for is to get to the
> > Control_Panel; I am instantiating ZClass instances in the constructor of a
> > Python class, i.e.:
> > 
> > class MyClass:
> > 
> >   def __init__(self, id, title=''):
> >       import Zope
> >       app = Zope.app()
> > 
> >       ob = app.Control_Panel.Products.MyProduct.MyZClass('newId')
> >       ob.id = 'newId'
> > 
> >       self._setObject('newId', ob)
> > 
> >       # Do I need a get_transaction().abort() here? Will that not abort
> >       # the wrong transaction?
> > 
> >       app._p_jar.close()
> > 
> 
> Hmm... you're creating an object in a separate connection (I would call
> get_transaction().abort() just to be on the safe side...) then copying
> that object over to the existing connection.  This will probably work,
> but I wouldn't be surprised to see thorny bugs appear.

I have just hit one such thorny bug. Oh well. :-)

> If you could instead get a handle to the existing connection, you'd be
> following standard practice.  You probably have a manage_addMyClass()
> method, don't you?  The "self" argument provided to that method is
> already connected to the database.  self.getPhysicalRoot() will give
> you the equivalent of the app object.  Then just change your
> constructor this way:
> 
> >   def __init__(self, app, id, title=''):
> >       ob = app.Control_Panel.Products.MyProduct.MyZClass('newId')
> >       ob.id = 'newId'
> > 
> >       self._setObject('newId', ob)

Yeah, I was there, and that worked great. Then, I started implementing my
__setstate__ method to "upgrade" old instances of my python class. I need
to access the connection from here, too, and this is where the trouble
begins.

AFAICT, I cannot call self.getPhysicalRoot() from __setstate__, for the
same reason I can't call it from __init__. I can get by the __init__
problem by passing app in as an argument from manage_addMyProduct(). I can
find no such solution for __setstate__.

> Best of luck!
> 
> Shane

All of my efforts are progressing towards one goal: How do I upgrade
existing instances of a ZClass? Since I could find no __setstate__ method
for ZClasses, I re-wrote the containing class as a Python class and
figured I could leverage __setstate__ there, instantiating the subordinate
ZClasses when required.

No such luck. 

I am going to spend a little more time working on this. If I can't find a
solution, I may drop ZClasses altogether and move all my code to Python. I
had hoped not to do this, because my web guys can work with ZClasses but
have no clue where to begin with a Python Product.

I may just have to take total ownership of the code, as much as I dislike
the idea, if I can find no other solution.

--Jeff

 ---
Jeff K. Hoffman 704.849.0731 x108
Chief Technology Officer                      mailto:jeff.hoffman@goingv.com
Going Virtual, L.L.C.                         http://www.goingv.com/