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TST value 0 vs Null ?

nipper

I am reading several values from Templates via DCRnode

i.e. $size = $rootnode->value('size');

Question, how do I distinguish size of 0 vs null (no entry) ? My only thought is to
look for <item name="size"> but that is a pain as I am looking for several parameters.

I cannot see a way to get this from the Perldoc but then my reading has never been
very good.

Andy

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Migrateduser

pel has a unary operator named defined which will tell you if a variable is defined or not

perldoc -f defined

if you want details.

And answer my email, darn it Smiley Wink

nipper

Cool

Thanks Rob.

& I will check email once my mail server decides to respond.

Andy

dazzlad

Be very careful about using defined.

Perl 5.82 gets rid of it and going through removing all occurences was one of the main pieces of work in upgrading our templates.

You can normally use:

if($variable) {

}

Adam Stoller

Not sure what you mean by "5.8.2 gets rid of [defined]" - I just did
perldoc -f defined on a TS6.1 system and got the following
results:

defined EXPR

@an_array)

@ary))

@_)

--fish
Senior Consultant, Quotient Inc.
http://www.quotient-inc.com

dazzlad

Ok.

Sorry. A bit hasty there.

I meant that it fails in presentation templates when used on iwpt_dcr_value (always returns true).

I shall make a mental note not to post anything before I've had a coffee.

Adam Stoller

No problem.

To get back to the original question:

If the intent here was to make sure that $size has a value of 0 if there's no value actually entered in the field - you could do something like:$size = $rootnode->value('size') || 0;In this case though I'd think that something like the following might do what is desired:$size = $rootnode->value('size');
if ($size eq ''){
# no value supplied
}
elsif ($size == 0){
# a value of zero supplied
}
else {
# a non-zero value supplied
# do you need to verify that it's > 0?
}

--fish
Senior Consultant, Quotient Inc.
http://www.quotient-inc.com

Migrateduser

I think we both need another cup of coffee, because I'm not understanding you. How exactly are you calling it?

If you call it as:

if (defined iwpt_dcr_value("foo"))

I would expect it to return true because it will actually check to see if the function iwpt_dcr_value is defined. Although, as I think about it, the same might apply in Andy's situation as well.

Here's a thought, you could try the type() method of XMLnode on an accessor string before you try value(). I would think that $node->type("foo") would return some variety of false value that would be a sound indicator that the node didn't actually exist.

Speaking of which,
if ($foo)

and
if (defined $foo)

are <b>emphatically not</b> identical.

Pontius Pilate once asked "what is truth?" Had I (or Larry Wall) been there, we might have answered: well, in perl, a true value is one of four things
1. a string of non-zero length
2. an integer value other than zero (including negative values)
3. a reference

undefined values are always false. However if you have
$a = 0; or $a ="";
and then try

if ($a) {

The condition will evaluate as false.

dazzlad

Hmm.

By way of illustration. Here is a code snippet from a current template running on our production system TS 5.52.

if (defined iwpt_dcr_value('dcr.pageType.normal')){
iwpt_output(qq(\n));
}
if (defined iwpt_dcr_value('dcr.pageType.customHTML')){
iwpt_output(qq(\n));
}
if (defined iwpt_dcr_value('dcr.pageType.framesPage')){
iwpt_output(qq(\n));
}
if (defined iwpt_dcr_value('dcr.pageType.extLink')){
iwpt_output(qq(\n));
}
if (defined iwpt_dcr_value('dcr.pageType.intLink')){
iwpt_output(qq(\n));
}
if (defined iwpt_dcr_value('dcr.pageType.shared')){
iwpt_output(qq(\n));
}
if (defined iwpt_dcr_value('dcr.pageType.popPage')){
iwpt_output(qq(\n));
}
if (defined iwpt_dcr_value('dcr.pageType.homePage')){
iwpt_output(qq(\n));
}
if (defined iwpt_dcr_value('dcr.pageType.indPage')){
iwpt_output(qq(\n));
}

When we brought our dev server up to TS 6.1 and tried to build one of these. each of the 'defined' statements evaluted to true. (result an html comment for every page type). It has been working fine in production with the defined keyword for years.

simply dropping the defined keyword *does* cause the conditional logic to work properly on TS 6.1.

Darren.

nipper

I was rather surprised when I noticed 6 new messages to this thread adter it was answered.
I have the case size = 0, size = snumber, and no size element in the XML.

$size = $rootnode->value('size');

By using if (undef $size) I get the case of no size element which is what I wanted.

I originally used if ($size) but that got the 0 as well as undefined.

Anyway, my issue was solved, back to our regularly scheduled diversions.....

Andy

Adam Stoller

By using if (undef $size) I get the case of no size element which is what I wanted.

I'm not sure that does what you want:

> iwperl -le 'my $size = 0; if (undef $size) { print "undef"; } else {print "defined($size)";}'
defined()
> perl -le 'my $size = undef; if (undef $size) { print "undef"; } else {print "defined($size)";}'
defined()
> iwperl -le 'my $size = 0; if (! defined($size)) { print "undef"; } else {print "defined($size)";}'
defined(0)
> perl -le 'my $size = undef; if (! defined($size)) { print "undef"; } else {print "defined($size)";}'
undef

--fish
Senior Consultant, Quotient Inc.
http://www.quotient-inc.com

nipper

Sorry you are correct I used (! defined ($size))

Andy