Jay Savage wrote:
On 4/25/06, JupiterHost.Net <[EMAIL PROTECTED]> wrote:
for my $obj(
sort {
$a->value() cmp $b->value()
||
$a->part('Name')->value() cmp $b->part('Name')->value()
}
grep { defined } @objects
) {
...
$a/$b->value() always works since if $a/$b is defined its an object with
a method called value()
$a/$b->part('Name') returns an object that also has a method called
value() or undefined if there is no "Name" part
The sort works perfect for what I need, *except* when
$a/$b->part('Name') does not return an object itself. Then it dies with
"Can't call method value() on undefined value."
So how can I keep my sort() but avoid/work with the "can't call method
on undefined value" error when $a/$b->part('Name') returns undef instead
of an object?
I've put them in valriables depending on defined()ness and done
$name_a cmp $name_b
Which is error free but also doesn't appear to sort it properly :(
How does it not sort properly? We need some sample data for that.
When using:
$a->part('Name')->value() cmp $b->part('Name')->value-()
in the sort funtion and all $a ans $b's part's have Names then it sorts
properly.
If I change it to
$name_a cmp $name_b
where $name_a and $name_n are set by a ternary check for definedness
and set to the method call's value or some default value if itd
undefined) it does not error out but not sort on $a or $b :)
Generally, though, you have two options. One is to trap the error with
eval or some other method. The other is to insert some logic to check
I'll havew to try that, eval since the logci just isn;t working :)
that the methods are defined before you call them...and decide how you
want to handle object that have no value. Perl is basically saying "I
can't sort it by value if it doesn't have a value". Either check for
definedness in the sort, or verify the data before you sort it and set
the bad data aside to deal with later.
This is one of the quirks of dealing with methods. If a method isn't
defined, it's more like an undefined subroutine call than an undefined
variable, in that attempting to call a method on an object for which
it's not defined is fatal.
HTH,
--jay
--------------------------------------------------
This email and attachment(s): [ ] blogable; [ x ] ask first; [ ]
private and confidential
daggerquill [at] gmail [dot] com
http://www.tuaw.com http://www.dpguru.com http://www.engatiki.org
values of β will give rise to dom!
--
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
<http://learn.perl.org/> <http://learn.perl.org/first-response>
