odd number of elements in anonymous hash - perl

Question

I'm trying to understand this Perl code...
If there is one stream it works, if there are 2 or more streams it warns with odd number of elements in anonymous hash. It seems to return an array in that case. How do I add the array elements correctly to #streams? It appears to add correctly for the HASH case in the if clause. Is the else clause bunk?
my $x = $viewedProjectDataObj->{streams};
if (ref($x) eq 'HASH') {
push(#streams, $x->{id});
} elsif (ref($x) eq 'ARRAY') {
print "$x\n";
print "#$x\n";
my #array = #$x;
foreach my $obj (#array) {
print "in $obj\n";
print Dumper( $obj);
push(#streams, ($obj->{id}) );
}
}
print "streamcount " . #streams % 2;
print Dumper(#streams);
my $stream_defect_filter_spec = {
'streamIdList' => #streams,
'includeDefectInstances' => 'true',
'includeHistory' => 'true',
};
my #streamDefects = $WS->get_stream_defects($defectProxy, \#cids, $stream_defect_filter_spec);
print Dumper(#streamDefects);
I'm adding the next lines...
if ($defectSummary->{owner} eq "Various") {
foreach (#streamDefects) {
if (exists($_->{owner})) {
$defectSummary->{owner} = $_->{owner};
last;
}
}
}
my $diref = $streamDefects[0]->{defectInstances};
if ($diref) {
my $defectInstance;
if (ref($diref) eq 'HASH') {
$defectInstance = $diref;
} elsif (ref($diref) eq 'ARRAY') {
$defectInstance = #{$diref}[0];
} else {
die "Unable to handle $diref (".ref($diref).")";
}
It now errors with
Web API returned error code S:Server: calling getStreamDefects: No stream found
for name null.
$VAR1 = -1;
me
Can't use string ("-1") as a HASH ref while "strict refs" in use at xyz-handler.pl line 317.
some Dumper output
$VAR1 = {
'streamIdList' => [
{
'name' => 'asdfasdfadsfasdfa'
},
{
'name' => 'cpp-62bad47d63cfb25e76b29a4801c61d8d'
}
],
'includeDefectInstances' => 'true',
'includeHistory' => 'true'
};

Answer 1

The list assigned to a hash is a set of key/value pairs, which is why the number of elements must be even.
Because the => operator is little more than a comma, and the #streams array is flattened in the list, this
my $stream_defect_filter_spec = {
'streamIdList' => #streams,
'includeDefectInstances' => 'true',
'includeHistory' => 'true',
};
is equivalent to this
my $stream_defect_filter_spec = {
'streamIdList' => $streams[0],
$streams[1] => $streams[2],
$streams[3] => $streams[4],
...
'includeDefectInstances' => 'true',
'includeHistory' => 'true',
};
so I hope you can see that you will get the warning if you have an even number of elements in the array.
To fix things you need the value of the hash element to be an array reference, which is a scalar and won't upset the scheme of things
my $stream_defect_filter_spec = {
'streamIdList' => \#streams,
'includeDefectInstances' => 'true',
'includeHistory' => 'true',
};
that way you can access the array elements as
$stream_defect_filter_spec->{streamIdList}[0]
etc.
And by the way you can tidy up your code substantially by letting map do what it's good at:
if (ref $x eq 'HASH') {
push #streams, $x->{id};
}
elsif (ref $x eq 'ARRAY') {
push #streams, map $_->{id}, #$x;
}

Answer 2

The assignment in:
my $stream_defect_filter_spec = {
'streamIdList' => #streams, # <---- THIS ONE
'includeDefectInstances' => 'true',
'includeHistory' => 'true',
};
is not correct, you get hash keys from the 1 3 5th ... array element.
You probably want assign a reference to array, not the array itself:
'streamIdList' => \#streams,
example for the unwanted (as in your code):
use strict;
use warnings;
use Data::Dump;
my #z = qw(a b c x y z);
dd \#z;
my $q = {
'aa' => #z,
};
dd $q;
unwanted result:
["a", "b", "c", "x", "y", "z"]
Odd number of elements in anonymous hash at a line 12.
{ aa => "a", b => "c", x => "y", z => undef }
^-here
Example of assign a reference
use strict;
use warnings;
use Data::Dump;
my #z = qw(a b c x y z);
dd \#z;
my $q = {
'aa' => \#z,
};
dd $q;
produces:
["a", "b", "c", "x", "y", "z"]
{ aa => ["a", "b", "c", "x", "y", "z"] }
The difference is clearly visible.