[Zope3-Users] Checking if an interface is provided by an object or could be adapted to

[Martin Aspeli]

Hi,

I'm probably doing something very wrong, but ...

I have a general interface that can either by directly provided by an  
object or class (typically with implements() on the class), but could also  
be provided via an adapter. I have a few places where I just need to check  
for this (it's not really a marker interface, but I need to know whether  
other code later on would be able to use the interface or not).

In my tests, I tried to use queryAdapter(), but that didn't return  
anything when the interface was implemented directly by the class.  
Similarly, Interface.providedBy() returns (expectedly) False if the  
interface could only be obtained via an adapter. Currently I do:

	  try:
             adapted = IFoo(context)
             return True
         except (ComponentLookupError, TypeError):
             return False

but that's just silly... Is there a pattern for this?

Martin

-- 
"You can just adapt yourself out of it..." // Archipelago sprint 26/04/2006