[Interface-dev] Chain adaption?

[Alexander Smith]

I do agree with you that it might be interesting if the component  
architecture could infer how to compose adapters, but I imagine the  
graph of possible adapter combinations could get quite large and  
complex.  I think for the sake of both efficiency and  
understandability, it's probably for the best to do adapter "chaining"  
manually.

To answer your second question,  I think your call to register an  
adapter is a little off.  It should be more like this:

    >>> zope.component.provideAdapter(BucketToCircle, ICircle, name='')

or even:

    >>>  zope.component.provideAdapter(BucketToCircle, ICircle)

Then to adapt a bucket instance:

    >>> bucket = Bucket()
    >>> circle_adapter = ICircle(bucket)

And to your third question, I think you're off to a solid start and  
asking some good questions.

Alexander J Smith
Software Engineer
Zope Corporation

On Jul 11, 2008, at 7:21 AM, Nitro wrote:

> Hello,
>
> I am trying to evaluate zope.interface for a project. What I want to  
> do is
> this: Let's assume I have something like
>
> class ICircle(zi.Interface):
>    radius = zi.Attribute("radius")
>
> class IEllipse(zi.Interface):
>    size = zi.Attribute("size")
>
> class Bucket(object):
>    litres = 10
>
> Now I define an adapter CircleToEllipse which can adapt ICircle to
> IEllipse objects (by doing size = (radius, radius)). Next I define  
> another
> adapter BucketToCircle which adapts a Bucket to an ICircle, by doing
> something like radius = litres. Finally, I want to be able to do  
> something
> like
>
> IEllipse( Bucket() )
>
> This doesn't work. The effect I'd like is zope.interface to chain the
> adaptions like Bucket -> BucketToCircle -> CircleToEllipse . I can  
> achieve
> this manually by doing
>
> myBucketAsEllipse = registry.queryAdapter( ICircle( Bucket() ),  
> IEllipse )
>
> But this is not really automatic. Related to this is that I am  
> unable to
> do:
>
> registry.register( [Bucket], ICircle, '', BucketToCircle )
>
> Instead I need to use adapter_hooks. This again seems to make chaining
> more of a trial-and-error process, because I can't tell  
> zope.interface to
> map Bucket to ICircle in a "rigid" way (the adapter hook can return
> different adapters depending on the object state for example).
>
> Attached is my working test file. It shows how everything is setup.
>
> 1) Does zope.interface support chaining?
> 2) Why does the register( [Bucket] ... ) call not work. I know  
> Bucket is
> not an interface, but it can be adopted to one.
> 3) Am I terribly misusing zope.interface?
>
> -Matthias
>
> P.S.: The wiki seems a bit outdated.
> http://wiki.zope.org/Interfaces/FrontPage and
> http://www.zope.org/Products/ZopeInterface/ should probably point to
> http://pypi.python.org/pypi/ 
> zope 
> .interface 
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