[Zope-dev] implementing zope.component 4.0

Shane Hathaway shane at hathawaymix.org
Mon Nov 30 17:33:26 EST 2009

Gary Poster wrote:
> Then to the multiadapter concern I raised, all my real-world examples
> of adapters are to adapt one object so it can be used in a certain
> way (to integrate with another kind of object).  Power adapters, for
> instance, adapt a plug (required interface) so it can plugged in to
> the wall (output interface).  Is there a common real-world example of
> this for "multiadapters"?

I have a Roku player (great device, BTW).  It streams video from Netflix 
and other sources.  It takes two inputs (network and power) and produces 
one output (a video signal).  I could call the device a multi-adapter, 
but the power input is so simple and reliable that I forget about it. 
Most of the time I think of the Roku player as a simple adapter from 
Internet packets to a video signal, but electrically, it's definitely a 

Note that the network signal for a Roku player varies wildly, while the 
power is either ~110VAC or ~220VAC.  Multi-adaptation works best when it 
has similar characteristics, I think.  It's safe to allow one of the 
inputs to multi-adaptation to vary a lot, but to keep developers sane, 
the rest of the inputs should be more predictable.  I think 
getMultiAdapter((context, request)) is OK because most web sites have 
only one or two request types.

> Turned around, people know the term "singleton" and they do not know
> the terms "adapters" and "utilities".  "singletons" describe the huge
> majority of how we use these things.  It's something less to explain.
> Making comprehension quicker is very valuable to me.

Do you intend to change the API names in zope.component, then?  For 
example, getUtility -> getSingleton?  That might be possible, but no one 
has suggested it before (AFAIK), and I think it's implied by your 

> ``IFoo.new(a, b)`` is equivalent to getMultiAdapter((a, b), IFoo)

Using "new" for a name could be a problem for Jython and IronPython 
users, since new is a keyword in other languages.


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