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From Andrew Jaquith <>
Subject Re: WikiContext switcheroos in Tag classes
Date Sat, 23 May 2009 13:55:44 GMT
Ok -- I checked in the code. In the refactored IteratorTag and
subclasses, the approach I took to context-switching was this:

- When an IteratorTag starts iterating, we keep a reference to the
current WikiContext in the private holding variable m_oldWikiContext.
Then we clone m_wikiContext and assign the clone to m_wikiContext.
Then, we stash the new (temporary) context in the request by calling
- When the IteratorTag finishes, we restore the old context by calling
WikiContextFactory.saveContext() again with m_originalContext.
- During iterations, the only thing that really changes is the
WikiPage. So we just let subclasses mess with the temporary context;
for example, calling setPage(). We do NOT clone it for every
iteration; there is frankly no need to do this.
- At all times, m_wikiContext retains the reference to the context
being rendered, same as always. However, we strongly discourage
subclasses from re-assigning this field; we let the parent IteratorTag
do all of this.

I think this is a pretty sensible approach. The most important aspect
of the refactoring is that we "pull up" responsibility for context
manipulation into IteratorTag. There is no longer a need for
subclasses to re-assign m_wikiContext.

There are a few small things that I still need to clean up, but for
the most part I'm happy with how it turned out.


On Fri, May 22, 2009 at 5:57 AM, Andrew Jaquith
<> wrote:
> HAH! I found the bastard. It's a cloning issue. WikiActionBeanContext wasn't
> cloning it's delegate DefaultWikiContext.
> Anyway, while I was at it, I refactored all of the iterator tags, whacking
> about 2/3 of the code (rampant cut-n-paste jobs). What I'll check in later
> will be lean, clean and documented. :)
> Andrew
> On May 21, 2009, at 14:20, Janne Jalkanen <> wrote:
>> It's likely that there is overlap in these techniques :-)
>> /janne, typing one-handedly
>> On 21 May 2009, at 21:03, Andrew Jaquith wrote:
>>>> My guess is that some of your other modifications are causing problems
>>>> with
>>>> the page names - on 2.8.x, the AttachmentsIteratorTag seems to be
>>>> working
>>>> perfectly.  Or maybe I misunderstood your problem?
>>> Yep, no question about it. Something isn't working as intended. I'll
>>> need to dig a bit to figure out what's going on. I'm going to be
>>> looking at a few issues: when m_wikiContext is actually changed; when
>>> ATTR_WIKICONTEXT is set, and when WikiContext.setPage() is called. Any
>>> of these three activities could be where the problem lies.
>>> Andrew

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