I was just going through that code ...

----- Original Message -----
From: "Jason Owens" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Wednesday, September 18, 2002 6:07 PM
Subject: Re: [Tapestry-developer] attach() not called


> Just found out some more interesting info:
>
> attach() *is* being called on the page, but it seems a component within
> the page is accessing a *different* instance of the same page (one that
> hasn't been initialized with an engine). The only connection between the
> page and component is the "model" parameter, which is specified as
> direction="in" and required="yes". Does Tapestry randomly grab components
> from the pool as well as pages, and then put them together for a render?

Does your "model" instance contain a reference to a page?  If it is
persistant (meaning it has a different lifecycle than the page it is on), it
should not.  Remember that persistent page state is *seperate* from page
instances.

Sounds like page instance B (attached to the engine) has a reference (inside
the model) to page instance A (which is still in the pool and in a detached
state).

You are going to have to rig things so that the model stores the *name* of
the page, and resolves it from the request cycle.  Alternately, you can
leverage some event notifications to set the page property of the model as
needed.

> If this is so, then the component/page relationship isn't being properly
> set.
> I'll try to look at the Tapestry code later tonight to see what I find,
> right now I've got plenty of other bugs to fix... (This does manifest more
> often when more than one person is using the app.)
> -Jason
>
>
> > I'll have to check into the PageLoader.  I know I moved
> > some stuff around, so that the engine property would be
> > set by the time that finishLoad() was invoked on a page,
> > or any component of the page.  I must have screwed
> > something up there.  Strangely, I do run Tapestry with
> > caching enabled but I haven't seen this!
> >
> > --
> > [EMAIL PROTECTED]
> >
> > http://tapestry.sf.net
> >> Hello all,
> >>
> >> I'm using 2.2b2, and seeing a very annoying effect:
> >>
> >> I visit a page, leave it for a while (visit some other pages,
> >> wait...), and then come back and get a NullPointerException. This
> >> isn't my error (though I may be causing it), since it's a null ENGINE!
> >> In fact, I've subclassed BasePage and overridden attach(), in order to
> >> determine what's going on, and it was never called. So in effect, I'm
> >> operating on a page that hasn't been attached. How can this be? Has
> >> anyone else seen this phenomenon?
> >> Any pointers would be appreciated...
> >>
> >> -Jason
> >>
> >>
> >>
> >>
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>
>
>
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