[Zope3-dev] Re: "most specific" interface?

[Jim Fulton]

Jean-Marc Orliaguet wrote:
...
> the idea is that you define as many categories as you need: IMetaType,
> ISomeCategory, IWidgetType ... and you create relations between
> interfaces with:
> 
>     directlyProvides(IFile, IContentType)

Exactly.

> as if you had a relation tool,

There are all sorts of ways of expressing relationships in Python
without central databases.

 > then every object that implements IFile
> (no matter in what position) will have the IFile content type?

Right.  Note that a content type is a specific kind of type.

If an object provides interface I, then the object is said to
be of type I.  If I is a content type, then the object is said
to have that content type.

As a matter of policy, we expect an object to have a single content
type and have a helper function for getting "the content type" by
finding an object's most specifiuc type that is a content type.

> But where do you put the 'directlyProvides' statement?

There are two options.  You put it in some python module, such
as the module that defines IFile:

   class IFile(...):
      ...

   directlyProvides(IFile, IContentType)

or, since this is often a configuration choice, you put in in
zcml:


   <interface
       interface=".interfaces.IFile"
       type="zope.app.content.interfaces.IContentType"
       />

Jim

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