[Interface-dev] zope.interface calling an interface with no arguments

[Daniel Krech]

On Aug 31, 2005, at 10:32 PM, Fred Drake wrote:

> On 8/31/05, Daniel Krech <eikeon at eikeon.com> wrote:
>
>> We're in the process of adding Interfaces to rdflib using Zope
>> Interfaces and also replacing rdflib's home brewed plugin system. So
>>
>
> Very cool!

Forgot to mention I'm really liking the interfaces... not sure how  
I've been coding in Python this long without them. Refreshing.

>> far things are going well, but we've run across something we'd like
>> to be able to do, namely, create an instance by calling the interface
>> with no arguments. For example:
>>
>
> This sounds like you're looking for more than just the interface
> definitions, but for something like the component architecture as well
> (zope.component).

True. Just keeping an eye on our dependencies. I'm thinking  
zope.component will probably be our next dependency  ;)

> The component architecture adds support for registries of objects that
> provide interfaces that can then be used as utilities.  The model that
> we'd follow would be to define an interface for a *factory* that
> creates objects of particular types.  A factory typically has one
> method (__call__), that takes whatever arguments are needed.  If there
> are different sets of arguments that may be passed, several methods
> can be defined for the factory interface, or different factory
> interfaces can be defined.  Code that wants to create objects of a
> certain interface looks up the corresponding factory interface (which
> it can do just once) and then use the factory to produce instances.
> Something like:
>
>     factory = zope.component.getUtility(IThingFactory)
>     thing_one = factory()
>     thing_two = factory()
>
> This has been working well so far in Zope 3; I think we're all really
> happy with it.  It might be worthwhile looking at zope.component from
> the Zope 3.1.0c2 release or from a Subversion checkout.

I'll take a look. Thank you.

>
>   -Fred
>
> -- 
> Fred L. Drake, Jr.    <fdrake at gmail.com>
> Zope Corporation
>

Daniel Krech, http://eikeon.com/