Using List::Util first on an array of Moose objects

Question

I have an array called aTestCaseList which is initialized and filled with (Moose) objects of type "Testcase". As expected I can print out the Attribute TestName of every Testcase Object in aTestCaseList. But when I try to find the first Object in the list named "Test4" using https://perldoc.perl.org/List/Util.html#first I get the following error

Can't call method "TestName" on an undefined value

Why are the objects in the array suddenly undefined?

use Testcase;

my @aTestcaseList=();
for (my $i=1; $i <= 9; $i++) {
  push(@aTestcaseList,Testcase->new("Test".$i));
}
my $sTestcase="Test4";
foreach my $sTestDummy(@aTestcaseList)
{
     #Works as expected and prints: Test1 Test2 Test3 ... Test9
     print $sTestDummy->TestName." "; 
} 
# throws the error:
my $sFindTest=first {$_->TestName eq $sTestcase} @aTestcaseList;

package Testcase;
use Moose;
use namespace::autoclean;

has 'TestName' => (is =>'ro',isa=>'Str');

around BUILDARGS => sub
{
    my $orig = shift;
    my $class = shift;

    if ( @_ == 1 && ! ref $_[0] ) {
        return $class->$orig(TestName => $_[0]);
    }
    else {
        return $class->$orig(@_);
    }
};
__PACKAGE__->meta->make_immutable;
1;

dgw · Accepted Answer · 2017-09-14 11:58:36Z

4

You forgot to import the function first from List::Util like

use List::Util qw(first);

answered Sep 14, 2017 at 11:58

dgw

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2 Comments

airborne Over a year ago

Yes, you are right. I think I did misinterpret the error message. I thought for some reason the objects itself are undefined.

ikegami Over a year ago

Without a declaration for first, first {$_->TestName eq $sTestcase} @aTestcaseList was interpreted as the (do {$_->TestName eq $sTestcase})->first(@aTestcaseList) indirect method call. $_ is undefined, so $_->TestName threw that error.

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