[Zope3-dev] Re: calling interface returns object, calling queryAdapter returns None?

[Marius Gedminas]

On Wed, Jan 24, 2007 at 08:44:31PM -0500, Tres Seaver wrote:
> Note that for regularity, I assert that the calling the IFoo interface
> should allow the follwing use cases, based on the asserition that
> utilities are "zero-order" adapters, just as views are "binary order"
> adapters.

There is a very important difference.

When you do adaptation, an adapter factory gets called and you get a new
object.  (There are exceptions -- the adapter factory may do caching, or
the object you're adapting may already implement the interface.)

When you do utility lookups, you always get the same object.  No factory
ever gets invoked.

Marius Gedminas
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