[Zope-CMF] [dev] content factories and events - a proposal

[Wichert Akkerman]

Previously yuppie wrote:
> Hi!
> 
> 
> We still have no easy way to use add views for CMF content. I tried to 
> figure out what needs to be done to make CMF content creation more 
> generic and to avoid duplicate notifyWorkflowCreated and (re)indexObject 
> calls.
> 
> 
> CMF uses two kinds of factories:
> 
> Oldstyle factories are used by FactoryTypeInformation if 'product' is 
> specified and by ScriptableTypeInformation. They are black box factory 
> methods that create unfinished content (no portal type set) and add it 
> to the container.
> 
> Newstyle factories are used by FactoryTypeInformation if 'product' is 
> not specified. They are zope 3 style factories. The code using these 
> factories is responsible for setting the portal type and adding the 
> content object to its container.
> 
> Both currently depend on the _finishConstruction() process that sets the 
> portal type and calls notifyWorkflowCreated() and reindexObject().
> 
> 
> Here are my assertions:
> 
> a) The right place for calling notifyWorkflowCreated() and indexObject() 
> is the event handler for IObjectAddedEvent. _setObject() sends this 
> event by default.
> 
> b) Oldstyle factory methods are not responsible for setting the portal 
> type. They call _setObject() to early for sending IObjectAddedEvent 
> because the portal type might be wrong at that moment.
> 
> 
> Proposed changes:
> 
> 1.) Let's get rid of _finishConstruction(): Using newstyle factories we 
> should set the portal type *before* calling _setObject(). 
> notifyWorkflowCreated() and reindexObject() should be called by the 
> event handler.
> 
> 2.) Fix *all* oldstyle factories: They don't finish content creation, so 
> they should not send the events. Since ScriptableTypeInformation factory 
> methods don't call _setObject() directly, this affects only file system 
> code.
>     self._setObject(id, o)
> Has to be replaced by:
>     self._setObject(id, o, suppress_events=True)
> In each factory of each third party content type. I don't like that, but 
> it is the only solution I see that allows us to use the events correctly.
> 
> 3.) For oldstyle factories, set the portal type after calling the 
> factory and send events after that. Unfortunately We can't send the 
> IObjectWillBeAddedEvent because we don't know the object before it is added.
> 
> 4.) For newstyle factories, also set the portal type, but let 
> _setObject() send the events.
> 
> 5.) Modify handleContentishEvent(): Add the notifyWorkflowCreated() call 
> for IObjectAddedEvent. indexObject() is already called.
> 
> 
> Any comments? Questions? Objections?

This change broke Plone: Plone has a routine that constructs new content
objects while bypassing parts of CMF which now breaks when it tries to
call _finishConstruction. 

Wichert.

-- 
Wichert Akkerman <wichert at wiggy.net>    It is simple to make things.
http://www.wiggy.net/                   It is hard to make things simple.