Using join to concatenate array values

Question

I have array values that is getting returned from SQL object.

my @keys = $db_obj->SelectAllArrayRef($sql);
print Dumper @keys;

gives

$VAR1 = [ [ '8853' ], [ '15141' ] ];

I need to create string from this array: 8853, 15141.

my $inVal = join(',', map { $_->[0] }, @$keys);

my $inVal;
foreach my $result (@$keys){
    $inVal .= $result->[0];
}

my $inVal = join(',', @$keys);

Value i get is ARRAY(0x5265498),ARRAY(0x52654e0). I think its reference to the array. Any idea what am I missing here?

my @keys = $db_obj->SelectAllArrayRef($sql); print Dumper @keys; Result from Dumper is $VAR1 = [ [ '8853' ], [ '15141' ] ]; — Kris1511
– Kris1511, Commented Jul 21, 2017 at 23:18
You would capture an array reference as my ($aref) = $db_obj->.... In perl, $keys and @keys are different variables (!). $keys is a scalar variable holding a value or a reference to something else. @keys is an array. See perldoc perlref for the gory details. — xxfelixxx
– xxfelixxx, Commented Jul 21, 2017 at 23:31
Your code doesn't produce the output you claim it does because @keys isn't the same as @$keys. — ikegami
– ikegami, Commented Jul 23, 2017 at 6:57

ikegami · Accepted Answer · 2017-07-23 07:00:04Z

2

Don't pass arrays to Dumper; it leads to confusing output. $VAR1 is not a dump of @keys, it's a dump of $keys[0]. Instead, you should have done

print(Dumper(\@keys));

This would have given

$VAR1 = [ [ [ '8853' ], [ '15141' ] ] ];

The code you want is

join ',', map { $_->[0] }, @{ $keys[0] };

That said, it appears that ->SelectAllArrayRef returns a reference to the result, and so it should be called as follows:

my $keys = $db_obj->SelectAllArrayRef($sql);

For this,

print(Dumper($keys));

outputs

$VAR1 = [ [ '8853' ], [ '15141' ] ];

And you may use either of the methods you used in your question.

join ',', map { $_->[0] }, @$keys;

edited Jul 23, 2017 at 7:00

answered Jul 23, 2017 at 6:49

ikegami

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xxfelixxx · Accepted Answer · 2017-07-21 23:01:39Z

2

The first version should work for you:

my $arr = [ [ '8853' ], [ '15141' ] ];
my $values = join(',', map { $_->[0] } @$arr);
print $values . "\n";

8853,15141

answered Jul 21, 2017 at 23:01

xxfelixxx

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2 Comments

Kris1511 Over a year ago

Doesn't seem to be working ...:( in the context... seems to work as script thought.

zdim Over a year ago

@Kris1511 Then show us that context please. Edit the question and show the code that sets this up. Otherwise, your first two attempts are good (the last one would give what you show, two reference-stringifications)

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