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Posted to user@velocity.apache.org by Philip Mark Donaghy <go...@yahoo.com> on 2003/11/20 12:52:09 UTC
last element in a foreach loop
Is there a way of knowing when we make the last loop
in a foreach class.
A variable velocityLast would make sense like the
variable velocityCount.
I need this so that I can avoid putting a comma(,)
behind the last element in the list.
How have you resolved this problem?
Thanks for the great techno,
Phil
=====
Java Web Application Architect
mapimage.com - Java and GIS
struts1.1:tomcat4.1.27:linuxRH8
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Re: last element in a foreach loop
Posted by "J. B. Rainsberger" <jb...@rogers.com>.
Tim Colson wrote:
> Say J.B. -
>
>
>>But why use more code? The version below captures what we really do:
>>
>>>>writeItem
>>>>loop starting at item #2
>>>> write comma; writeItem
>>>>endloop
>
> Uh... no offense, but that's pseudo-code, not a real template snippet.
> The various other answers were pretty clear. But this one is clear only
> in theory, not sure what the actual template would look like. (Heck, I
> don't even know how to start a loop for $LIST_OF_THINGIES at item #2 in
> a #foreach.)
Well, I was arguing /clear/, not /legal/. :)
No, it's an excellent point: the discussion's not worth much if I throw
in code that can't work. I'm still getting used to Velocity.
This points to a feature not present in the VTL: the ability to join an
array. I would tend to implement that as a tool rather than try to bend
VTL to my will. Were we talking about JSP, I'd have implemented a custom
tag.
An "if" statement that evaluates one way potentially 99% of the time
(for 100-item list) is questionable and perhaps best eliminated, not to
mention the sheer amount of code one would duplicate if one were to
copy-and-paste that loop rather than implement it in a macro.
--
J. B. Rainsberger,
Diaspar Software Services
http://www.diasparsoftware.com :: +1 416 791-8603
Let's write software that people understand
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RE: last element in a foreach loop
Posted by Tim Colson <tc...@cisco.com>.
Say J.B. -
> But why use more code? The version below captures what we really do:
> >>writeItem
> >>loop starting at item #2
> >> write comma; writeItem
> >>endloop
Uh... no offense, but that's pseudo-code, not a real template snippet.
The various other answers were pretty clear. But this one is clear only
in theory, not sure what the actual template would look like. (Heck, I
don't even know how to start a loop for $LIST_OF_THINGIES at item #2 in
a #foreach.)
Timo
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RE: last element in a foreach loop
Posted by Dave Newton <da...@solaraccess.com>.
On Fri, 2003-11-21 at 01:05, Shawn Church wrote:
> > This sentence nearly caused me to pull off my own head and reminds me of
> > a funny web page I recently read about the perils of "academic prose."
> But, but, well, um, yes, ok, I see your point.
;)
> So you are including presentation elements in macros?
Yeah, I do sometimes, as I reuse them a lot... I've never been sure if
that's a good idea or not, really, and I've "lost" view element
definitions at times.
Then I tried naming conventions, like "viewItemRow" and things like
that. It sorta-solved that, and that's where it stands for now :)
Dave
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RE: last element in a foreach loop
Posted by Shawn Church <sh...@boxity.com>.
> > A low cyclomatic
> > complexity contributes to a programs amenability to
> modification at lower
> > risk.
>
> This sentence nearly caused me to pull off my own head and reminds me of
> a funny web page I recently read about the perils of "academic prose."
>
> :)
But, but, well, um, yes, ok, I see your point.
>
>
> > This example was loosely pulled from one of my actual
> templates, and there
> > are in fact over 80 html lines involved within this particular #foreach
> > block. If I decide to add a column in the table or to
> otherwise change its
> > presentation, I would stand a good chance of breaking the page.
> There's no
> > good reason I would want to duplicate these lines.
>
> That's why they invented macros, I suppose, which has the additional
> benefit (in theory, of course) of not embedding stuff far down a page,
> and might also allow a similar presentation style across pages.
I will give this a try, but I usually #parse things like this. I've used
macros mainly to wrap calls to context tools which require further validity
checking or response handling. I don't normally include any html or other
view-related things in macros, but rather only use them to hide sequences of
necessary but busy Velocity tags. So you are including presentation
elements in macros?
Shawn
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RE: last element in a foreach loop
Posted by Dave Newton <da...@solaraccess.com>.
On Thu, 2003-11-20 at 20:19, Shawn Church wrote:
> A low cyclomatic
> complexity contributes to a programs amenability to modification at lower
> risk.
This sentence nearly caused me to pull off my own head and reminds me of
a funny web page I recently read about the perils of "academic prose."
:)
> #foreach( $item in $itemlist)
> <div class=...>
> <tr>
> <td nowrap>
> <table border="0" cellspacing="0" cellpadding="2">
> <tr>
> <td><a href="xxx">$item.yyy</a></td>
> <td>
> <form action="zzz" method="post" name="zzz" >
> <input type="hidden" name="aaa" value="$item.yyy">
> <input type="image" name=submit.details value="Details"
> src="/images/details.gif" border=0 alt="Details">
> </form>
> </td>
> </tr>
> </table>
> </td>
> </tr>
> </div>
> #end
>
> This example was loosely pulled from one of my actual templates, and there
> are in fact over 80 html lines involved within this particular #foreach
> block. If I decide to add a column in the table or to otherwise change its
> presentation, I would stand a good chance of breaking the page. There's no
> good reason I would want to duplicate these lines.
That's why they invented macros, I suppose, which has the additional
benefit (in theory, of course) of not embedding stuff far down a page,
and might also allow a similar presentation style across pages.
Dave
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Re: last element in a foreach loop
Posted by "J. B. Rainsberger" <jb...@rogers.com>.
Shawn Church wrote:
> More cyclomatic complexity? I respectfully disagree.
Um, more if statements means higher cyclomatic complexity, does it not?
Is 1 no longer greater than 0? (It's possible I have the wrong
definition of cyclomatic complexity, but I don't think so...)
<snip/>
> Duplicating sections of code such as 'writeItem' is generally a bad idea,
> and one which I tend to avoid if possible. This is true regardless of the
> type of code, whether in a Velocity template, Java source, or whatever.
> Everything from subroutines and functions in procedural languages to methods
> and procedures in more object-oriented languages lend themselves to the
> elimination of redundant code. Maybe your 'writeItem' is in fact a single
> line, but most commonly for me in the generation of html data streams
> 'writeItem' actually represents something more like this kind of business:
<snip />
If I need to be a single line, it becomes a single line. That's why we
have macros, no?
> This example was loosely pulled from one of my actual templates, and there
> are in fact over 80 html lines involved within this particular #foreach
> block. If I decide to add a column in the table or to otherwise change its
> presentation, I would stand a good chance of breaking the page. There's no
> good reason I would want to duplicate these lines.
I wouldn't dream of duplicating 80 lines. One line, though, duplicated
within two lines of its duplicate... I think most programmers can handle
that. :)
> My method is only an example, and Barbara's use of $velocityCount is
> actually cleaner and preferable in most instances, especially if you are
> concerned with the complexity of an #if #else block.
Clearly our opinions differ. That's OK: it makes the world go round.
--
J. B. Rainsberger,
Diaspar Software Services
http://www.diasparsoftware.com :: +1 416 791-8603
Let's write software that people understand
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RE: last element in a foreach loop
Posted by Shawn Church <sh...@boxity.com>.
More cyclomatic complexity? I respectfully disagree. A low cyclomatic
complexity contributes to a programs amenability to modification at lower
risk.
Duplicating sections of code such as 'writeItem' is generally a bad idea,
and one which I tend to avoid if possible. This is true regardless of the
type of code, whether in a Velocity template, Java source, or whatever.
Everything from subroutines and functions in procedural languages to methods
and procedures in more object-oriented languages lend themselves to the
elimination of redundant code. Maybe your 'writeItem' is in fact a single
line, but most commonly for me in the generation of html data streams
'writeItem' actually represents something more like this kind of business:
#foreach( $item in $itemlist)
<div class=...>
<tr>
<td nowrap>
<table border="0" cellspacing="0" cellpadding="2">
<tr>
<td><a href="xxx">$item.yyy</a></td>
<td>
<form action="zzz" method="post" name="zzz" >
<input type="hidden" name="aaa" value="$item.yyy">
<input type="image" name=submit.details value="Details"
src="/images/details.gif" border=0 alt="Details">
</form>
</td>
</tr>
</table>
</td>
</tr>
</div>
#end
This example was loosely pulled from one of my actual templates, and there
are in fact over 80 html lines involved within this particular #foreach
block. If I decide to add a column in the table or to otherwise change its
presentation, I would stand a good chance of breaking the page. There's no
good reason I would want to duplicate these lines.
My method is only an example, and Barbara's use of $velocityCount is
actually cleaner and preferable in most instances, especially if you are
concerned with the complexity of an #if #else block.
Shawn
-----Original Message-----
From: J. B. Rainsberger [mailto:jbrains@rogers.com]
Sent: Thursday, November 20, 2003 4:38 PM
To: Velocity Users List
Subject: Re: last element in a foreach loop
Shawn Church wrote:
> Adding a little more code but avoiding the extra writeItem, you could
> also do:
>
> #set($first = true)
> #foreach($item in $itemlist)
> #if($first)
> #set($first = false)
> #else
> write comma
> #end
> write $item
> #end
But why use more code? The version below captures what we really do:
write an item, then (write a comma, write an item) until there are no
more items. It deals with its special case simply.
The above version is more code, more cyclomatic complexity and less
clear, at least at first glance.
Nothing bad about you, mind... I just think that above solution is
unnecessarily complicated.
>>writeItem
>>loop starting at item #2
>> write comma; writeItem
>>endloop
--
J. B. Rainsberger,
Diaspar Software Services
http://www.diasparsoftware.com :: +1 416 791-8603
Let's write software that people understand
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Re: last element in a foreach loop
Posted by "J. B. Rainsberger" <jb...@rogers.com>.
Shawn Church wrote:
> Adding a little more code but avoiding the extra writeItem, you could
> also do:
>
> #set($first = true)
> #foreach($item in $itemlist)
> #if($first)
> #set($first = false)
> #else
> write comma
> #end
> write $item
> #end
But why use more code? The version below captures what we really do:
write an item, then (write a comma, write an item) until there are no
more items. It deals with its special case simply.
The above version is more code, more cyclomatic complexity and less
clear, at least at first glance.
Nothing bad about you, mind... I just think that above solution is
unnecessarily complicated.
>>writeItem
>>loop starting at item #2
>> write comma; writeItem
>>endloop
--
J. B. Rainsberger,
Diaspar Software Services
http://www.diasparsoftware.com :: +1 416 791-8603
Let's write software that people understand
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Re: last element in a foreach loop
Posted by Shawn Church <sh...@boxity.com>.
Adding a little more code but avoiding the extra writeItem, you could
also do:
#set($first = true)
#foreach($item in $itemlist)
#if($first)
#set($first = false)
#else
write comma
#end
write $item
#end
Quoting "J. B. Rainsberger" <jb...@rogers.com>:
> Philip Mark Donaghy wrote:
>
> > Is there a way of knowing when we make the last loop
> > in a foreach class.
> >
> > A variable velocityLast would make sense like the
> > variable velocityCount.
> >
> > I need this so that I can avoid putting a comma(,)
> > behind the last element in the list.
> >
> > How have you resolved this problem?
>
> The other way around: loop like so.
>
> writeItem
> loop starting at item #2
> write comma; writeItem
> endloop
>
> You /know/ when you're at the first element, which is easier than
> what
> you're trying to do.
> --
> J. B. Rainsberger,
> Diaspar Software Services
> http://www.diasparsoftware.com :: +1 416 791-8603
> Let's write software that people understand
>
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: velocity-user-unsubscribe@jakarta.apache.org
> For additional commands, e-mail:
> velocity-user-help@jakarta.apache.org
>
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Re: last element in a foreach loop
Posted by "J. B. Rainsberger" <jb...@rogers.com>.
Philip Mark Donaghy wrote:
> Is there a way of knowing when we make the last loop
> in a foreach class.
>
> A variable velocityLast would make sense like the
> variable velocityCount.
>
> I need this so that I can avoid putting a comma(,)
> behind the last element in the list.
>
> How have you resolved this problem?
The other way around: loop like so.
writeItem
loop starting at item #2
write comma; writeItem
endloop
You /know/ when you're at the first element, which is easier than what
you're trying to do.
--
J. B. Rainsberger,
Diaspar Software Services
http://www.diasparsoftware.com :: +1 416 791-8603
Let's write software that people understand
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Re: last element in a foreach loop
Posted by Hans Juergen von Lengerke <le...@sixt.de>.
> Is there a way of knowing when we make the last loop
> in a foreach class.
This is what I use:
#foreach ($item in $items)
#if ($velocityCount == $items.size() - 1)
Last Item: $item
#end
#end
(This assumes that you have configured
directive.foreach.counter.initial.value = 0)
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Re: last element in a foreach loop
Posted by Barbara Baughman <ba...@utdallas.edu>.
For comma separations of a list, I use:
#foreach ($item in $items)
#if (velocityCount>1),#end $item
#end
This puts a comma-blank before all but the first $item. To avoid line
breaks, put it all on one line.
Barbara Baughman
X2157
On Thu, 20 Nov 2003, Philip Mark Donaghy wrote:
> Is there a way of knowing when we make the last loop
> in a foreach class.
>
> A variable velocityLast would make sense like the
> variable velocityCount.
>
> I need this so that I can avoid putting a comma(,)
> behind the last element in the list.
>
> How have you resolved this problem?
>
> Thanks for the great techno,
> Phil
>
> =====
> Java Web Application Architect
> mapimage.com - Java and GIS
> struts1.1:tomcat4.1.27:linuxRH8
>
> __________________________________
> Do you Yahoo!?
> Free Pop-Up Blocker - Get it now
> http://companion.yahoo.com/
>
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>
>
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