[Zope-dev] Acquisition wishlist :-)

[Martijn Pieters]

On Thu, Jan 04, 2001 at 10:46:35AM +0000, Chris Withers wrote:
> Dieter Maurer wrote:
> > 
> >  >      acquisition.donotacquire('index_html')
> > This would be great.
> 
> Indeed :-)
> 
> >  > class MyClass (Acquisition.Explicit):
> >  >
> >  >      acquisition = ClassAcquisitionInfo()
> >  >
> >  >      acquisition.acquire('index_html')
> >  >      acquisition.acquire('fred')
> > You already can do that, though with a different syntax
> > (I would need to search for in the documentation).
> 
> You may mean that if x is an Acquisition.Explicit object, you can do:
> 
> x.aq_acquire('your_attribute') (syntax may be wrong ;-)
> 
> What I meant is that through a declaration in the class you could saying
> acquire the 'your_attribute' attribute but nothing else. So, you could
> still do:
> 
> x.your_attribute ...which would be acquired, but...
> x.index_html     ...which wouldn't be acquired.

You could use ComputedAttribute for that:

class MyClass(Acquisition.Explicit):
    # The following attribute is acquired transparently
    def _acquired_your_attribute(self):
    	return self.aq_acquire('your_attribute')
    your_attribute = ComputedAttribute(_acquired_your_attribute, 1)

    # index_html isn't
    index_html = None

Or you could define a __getattr__ that does a lookup in a list for
explicetly acquired attributes:

    _acquired = ('index_html', 'fred')
    def __getitem__(self, key):
        if key in self._acquired:
	    return self.aq_acquire(key)
	raise AttributeError, name

-- 
Martijn Pieters
| Software Engineer  mailto:mj@digicool.com
| Digital Creations  http://www.digicool.com/
| Creators of Zope   http://www.zope.org/
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