[Zope3-dev] Re: Heads up: major event changes

[Jim Fulton]

This is checked in.  For some reason, the checkin mailer missfired on this
one and there was no mail to zope3-checkins.  (Although, perhaps the
message is just being delayed due to it's size.)

Jim

Jim Fulton wrote:
> 
> This morning I'll be checking in a major simplification of Zope 3's event
> system, http://dev.zope.org/Zope/SimplifyEventSystem.
> 
> The major change for application developers:
> 
> 1. Any object can be an event
> 
> 2. You publish events like this:
> 
>      from zope.event import notify
> 
>      ...
> 
>      notify(event)
> 
>    Calling zope.app.event.publish still works, but generates a
>    deprecation warning.
> 
> 3. Event handlers are now defined as functions.  For example, before:
> 
>       from datetime import datetime
>       from zope.app.dublincore.interfaces import IZopeDublinCore
>       from zope.app.event.interfaces import ISubscriber
>       from zope.interface import implements
> 
>       class DCTimeAnnotatorBase:
>           """Update Dublin-Core time property
>           """
>           implements(ISubscriber)
> 
>           def notify(self, event):
>               dc = IZopeDublinCore(event.object, None)
>               if dc is not None:
>                   self.annotate(dc)
> 
>           def annotate(self, dc):
>               raise RuntimeError, 'annotate not implemented'
> 
> 
>       class ModifiedAnnotatorClass(DCTimeAnnotatorBase):
>           """Updates DC modified when an object is modified."""
> 
>           def annotate(self, dc):
>               dc.modified = datetime.utcnow()
> 
> 
>       class CreatedAnnotatorClass(DCTimeAnnotatorBase):
>           """Sets DC created and modified when an object is created."""
> 
>           def annotate(self, dc):
>               now = datetime.utcnow()
>               dc.created = now
>               dc.modified = now
> 
> 
>       ModifiedAnnotator = ModifiedAnnotatorClass()
>       CreatedAnnotator = CreatedAnnotatorClass()
> 
>    After:
> 
>       from datetime import datetime
>       from zope.app.dublincore.interfaces import IZopeDublinCore
> 
>       def ModifiedAnnotator(event):
>           dc = IZopeDublinCore(event.object, None)
>           if dc is not None:
>               dc.modified = datetime.utcnow()
> 
>       def CreatedAnnotator(event):
>           dc = IZopeDublinCore(event.object, None)
>           if dc is not None:
>               now = datetime.utcnow()
>               dc.created = now
>               dc.modified = now
> 
>    :)
> 
>    Handlers are also registered differently in ZCML.  There are no longer
>    event:subscriber directives. Rather, subscriber directoves from the zope
>    namespace are used, as in:
> 
>       <subscriber
>           for="zope.app.event.interfaces.IObjectModifiedEvent"
>           factory=".timeannotators.ModifiedAnnotator"
>           />
> 
>       <subscriber
>           for="zope.app.event.interfaces.IObjectCreatedEvent"
>           factory=".timeannotators.CreatedAnnotator"
>           />
> 
> Jim
> 


-- 
Jim Fulton           mailto:jim at zope.com       Python Powered!
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