[Zope-dev] bug in zpatterns-0.4 ?

[mike]

Jephte CLAIN wrote:
> 
> mike wrote:
> > Jephte CLAIN wrote:
> > > Rack.createItem (low level method) first calls Rack.getItem (higher
> > > level method) to check the existence of the item.
> > > This causes infinite loop in certain cases. It should (IMHO) call
> > > Rack.retrieveItem instead
> > Could you provide an example please?
> My data is located in an SQL database. I want to have some associated
> data in ZODB. ZPatterns is a perfect fit for this. When I first access a
> SQL record, the corresponding data is created in ZODB:
> 
> def getItem(self, key):
>   if self.sql_get(key=key):
>     # ok it exists in the SQL database
>     item = Rack.getItem(self, key)
>     if item is None:
>       # it does not exist in ZODB, create it
>       item = Rack.newItem(self, key)
>   else:
>     item = None
>   return item
> 
> This causes infinite loop because Rack.newItem calls Rack.createItem
> which calls my (modified) getItem

1. Leave getItem untouched. Move all that SQL-related stuff into the
retrieveItem method which *is intended* to be overriden. 

2. Move newItem stuff into Specialist. You have mixed 'Restaurant' and
the 'FoodStore' in this snippet :-) Do this instead:

Specialist:

  def getItem( self, key) :
    item = self._src().getItem( key)
    if item is None :
      item = self._src().newItem( key)
    return item

  def _src( self) :
    return self.rackList[0].__of__( self)


Rack:
  
  def retrieveItem( self, key) :
    item = self.sql_get( key)
    blah blah blah ...
    return item
  
Mike