[Grok-dev] Simple adapter question
optilude+lists at gmail.com
Thu Mar 5 14:26:16 EST 2009
Carsten Senger wrote:
> Hallo Jan,
> Jan Ulrich Hasecke schrieb:
>> -----BEGIN PGP SIGNED MESSAGE-----
>> Hash: SHA1
>> browsing the docs I have a question concerning adapters.
>> import grok
>> from zope import interface
>> class Fireplace(grok.Model):
>> class Cave(grok.Model):
>> class IHome(interface.Interface):
>> class Home(grok.MultiAdapter):
>> grok.adapts(Cave, Fireplace)
>> def __init__(self, cave, fireplace):
>> self.cave = cave
>> self.fireplace = fireplace
>> home = IHome(cave, fireplace)
This looks fishy to me. Unless Grok is doing something very evil, this
won't work: it'll try to adapt `cave` to IHome, and if that fails, it'll
fall back to the second argument 'fireplace'.
I think what you want is:
home = getMultiAdapter((cave, fireplace), IHome)
>> Why is there an IHome in the last line? I would think that
>> home = Home(cave, fireplace)
>> would create a home-instance.
It does, and in this case, the two are probably equivalent. "Calling"
the interface (for a single-adapter!) or using
getAdapter/getMultiAdapter, means "Get the adapter from what I give you,
to the interface I ask for". If there was a more specific adapter to
IHome, then you'd get that one instead.
If you can, find Brandon Craig Rhodes "using grok to walk like a duck"
talk on video and watch it. :)
Author of `Professional Plone Development`, a book for developers who
want to work with Plone. See http://martinaspeli.net/plone-book
More information about the Grok-dev