RE: Map.get(missingKey) doesnt return null.

[Steve O'Hara]

I think I'm right in thinking that this is correct behaviour according
to the documentation.
Velocity never assigns null - there isn't a mechanism for assigning null
to a variable in VTL.
However, if the result of a computation or set statement would be null,
then the assignment is ignored.

So, the correct way of achieving what you want is this;

#foreach ($student in students)
        #if ($storedTimes.get($student.getID()))
                #set($storedMap = $storedTimes.get($student.getID()))
                $student.getID() $storedMap <br>
      #end
#end 


As an aside, I've stumbled over this behaviour before and would like it
if it can be changed so that you can assign null to a variable - what
are the thoughts of others (and the code contributors)?

Steve


-----Original Message-----
From:
[EMAIL PROTECTED]
.org
[mailto:[EMAIL PROTECTED]
a.apache.org] On Behalf Of Daniel Brownell
Sent: 29 September 2005 23:49
To: Velocity Users List
Subject: Map.get(missingKey) doesnt return null. 

Hi there,

Thanks for the help on the Map of maps question.  This question is
related.  
Velocity is giving me values when I should be getting null.

Here is the code:

#foreach ($student in students)
        #set($storedMap = $storedTimes.get($student.getID()))
        $student.getID() $storedMap <br>
#end

In the output below, 6 of the students are'nt actually mapped in
$storedMap.
Only the first of the students with sh=10, sh=1 or sh=6 are actually in
my HashMap. (ie. 492,493,496,497 are using 491's value.)

For some reason, the value of $storedMap is not updated to be null, as
it should, and I get stragglers copying values that aren't theirs.  My
check for null is useless because Velocity is not behaving.

581502 {sh=7, eh=7, sa=PM, ea=PM, sm=30, em=00}
581503 {sh=8, eh=7, sa=PM, ea=PM, sm=30, em=00}
581504 {sh=9, eh=7, sa=PM, ea=PM, sm=30, em=00}
581491 {sh=10, eh=7, sa=PM, ea=PM, sm=30, em=00}
581492 {sh=10, eh=7, sa=PM, ea=PM, sm=30, em=00}
581493 {sh=10, eh=7, sa=PM, ea=PM, sm=30, em=00}
581496 {sh=10, eh=7, sa=PM, ea=PM, sm=30, em=00}
581497 {sh=10, eh=7, sa=PM, ea=PM, sm=30, em=00}
581505 {sh=1, eh=6, sa=AM, ea=PM, sm=30, em=15}
581506 {sh=1, eh=6, sa=AM, ea=PM, sm=30, em=15}
581507 {sh=6, eh=6, sa=AM, ea=PM, sm=30, em=30}
581508 {sh=6, eh=6, sa=AM, ea=PM, sm=30, em=30}
581495 {sh=6, eh=6, sa=AM, ea=PM, sm=30, em=30}

Thanks
Dan

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