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From "Van Riper, Mike" <mvanri...@verisign.com>
Subject RE: iterate question
Date Wed, 04 Sep 2002 22:20:47 GMT
I have a similar need to the one expressed by Kirby. I have not used the
nested extension, but, I have read through the online primer. I saw nothing
there that would indicate it would handle *dynamic* tree structures. Yes,
you can use the nesting custom tags to any depth you want. Yes, you don't
need to know in advance how many items there are in a collection at a
particular level. However, it looks like you need to know in advance what
depth to go to. When the tree is being generated dynamically and the depth
can not be known in advance, I don't see how to use the nesting extension to
handle it.

I hope that I am wrong about that because I'd love to just use the nesting
extension rather than write something on my own. If the nesting extension
can handle this situation, please point me to the right part of the docs or
an existing example that will help me figure that out.

Assuming I am right and the nesting extension doesn't handle what I need
yet, my sense is there might be a way to enhance the nesting extension to
handle this for recursive structures. For example, consider a Node object
that had some instance data and a collection of child Node objects and a
getChildNodes() method. What if <nested:iterate> took an additional
parameter which was recurseProperty="childNodes"? It should be possible to
implement tail recursion in the implementation of <nested:iterate> that
would repeat the execution of the body of the <nested:iterate> tag with the
new collection being the one returned from the getChildNodes() call on the
current node. This would do a depth first recursion of nodes outputting the
same information for each node. Assuming there is a way to get depth
information, I could use that information in the body of my <nested:iterate>
and dynamically reflect that in the formatting of the nodes for display too.

Of course, it is not that simple. There would be intermediate state to
maintain and correctly return to and continue on from for each time a
recursion to another level happened. The nesting extension does quite a bit
already and this may not be the best way to solve my recursive structure
handling problem. Then again, maybe it would make sense. I thought it was at
least worth sharing the idea.

- Mike Van Riper
  mailto:mvanriper@verisign.com

> -----Original Message-----
> From: Sri Sankaran [mailto:Sri.Sankaran@sas.com]
> Sent: Wednesday, September 04, 2002 11:29 AM
> To: Struts Users Mailing List
> Subject: RE: iterate question
> 
> 
> Look at the nested extension @ 
> http://www.keyboardmonkey.com/next/index.jsp.  It is exactly 
> for this purpose.
> 
> It is included as part of Struts 1.1.x
> 
> Sri
> 
> > -----Original Message-----
> > From: Kirby Vandivort [mailto:kvandivo@ks.uiuc.edu] 
> > Sent: Wednesday, September 04, 2002 12:13 PM
> > To: struts-user@jakarta.apache.org
> > Subject: iterate question
> > 
> > 
> > Hello,
> > 
> > I'm new to struts, so please bear with me.  I'm in the early 
> > stages of converting something to the struts framework and 
> > I've run into a situation that I'm not sure how to handle.
> > 
> > I want to make a page that, as an example, looks like:
> > 
> >   - message 1
> >   - message 2
> >     * re: message 2
> >       + re: re: message 2
> >     * re: message 2
> >     * re: message 2
> >   - message 3
> > 
> > 
> > etc.  So, I'm going to pass a collection to the jsp page, and 
> > the collection might contain collections.  There can be any 
> > level of nesting.  
> > 
> > This seems like a common case, but I haven't found a way to 
> > do it using the struts tags as of yet.  It really needs some 
> > sort of recursive solution since you don't know how many 
> > levels you will need to go down, and the presentation is 
> > something that clearly shouldn't be done on the business 
> > side, so any help or guidance that you have would be appreciated.
> > 
> > Thanks!
> > 
> > -- 
> > 
> > Kirby Vandivort                      Theoretical Biophysics Group
> > Email: kvandivo@ks.uiuc.edu          3051 Beckman Institute
> > http://www.ks.uiuc.edu/~kvandivo/    University of Illinois
> > Phone: (217) 244-5711                405 N. Mathews Ave
> > Fax  : (217) 244-6078                Urbana, IL  61801, USA
> > 
> > --
> > To unsubscribe, e-mail:   
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> > For 
> > additional commands, 
> > e-mail: <mailto:struts-user-help@jakarta.apache.org>
> > 
> > 
> 

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