[Zope3-Users] How come no IView?

[Wade Leftwich]

Chris McDonough wrote:
> It will probably not comfort you that the concept of a "view" (at  least
> by that name) is going to disappear sometime post-3.2.
> 
> I hope I explain this properly; here goes.
> 
> A view is a registration for a "named multiadapter".  The thing that  is
> registered ("the view") adapts two objects that implement  interfaces to
> a different interface.  Part of what makes a "view" a  "view" is that
> it's registered to accept two objects in its factory:  a content object
> and a request object.  Another kind of "named  multiadapter" might
> accept three, four, or five objects in its  factory.  A view happens to
> accept two, and only by convention are  these two objects that are
> "context" and "request" objects.
> 
> When you look up a "view", the two objects you pass to  "getView"
> (context and request) conventionally implement,  respectively,
> IBrowserRequest and a content class interface.
> There is a class registered to adapt them to a marker interface 
> (zope.Interface).  So when a view is looked up like this:
> 
> from zapi import getView
> from zope.interface import Interface
> from zope.interface import implements
> from zope.publisher.interfaces.browser import IBrowserRequest
> 
> class IContent(Interface):
>     pass
> class Content(object):
>     implements(IContent)
> content = Content()
> class Request(object):
>     implements(IBrowserRequest)
> request = Request()
> 
> getView(content, u'index.html', request)
> 
> ... under the hood the lookup is translated to:
> 
> getMultiAdapter((content, request), Interface, name=u'index.html')
> 
> ... and you get back a view class instance.  The view class  constructor
> is passed "content" and "request" in its constructor  because that's
> what getMultiAdapter is wired to do.  If you were  adapting more than
> two, the class constructor would be passed three,  or four, etc.
> 
> This is because the registration of a view class (when it happens via 
> ZCML) is essentially:
> 
> from zope.component import registerAdapter
> 
> class SomeView(object):
>     def __init__(self, context, request):
>         self.context = context
>         self.request = requests
> 
> registerAdapter(SomeView, (IContent, IBrowserRequest), Interface, 
> name=u'index.html')
> 
> The concept of a "view" is purely convention.  getView is actually 
> deprecated in the trunk at least, as a result.  I don't know if that 
> makes anything clearer but I for one welcome our new simplification 
> overlords.
> 

Thanks Chris, that actually does make things clearer. As a Z3 beginner,
longtime Z2 user (ZPTs, scripts, ZSQL), and corporate developer who is
trying to promote Z3 in-house, I am all for the current  trend toward
simplification, especially of ZCML
(http://www.z3lab.org/sections/blogs/philipp-weitershausen/2005_12_14_zcml-needs-to-do-less).

It seems like "view class" is a useful concept that gets talked about a
lot. We're not going to have to start saying "named multiadapter for
content and request", are we?

-- Wade