How do I determine the number of elements in an array reference?

Question

Here is the situation I am facing...

$perl_scalar = decode_json( encode (\'utf8\',$line));

decode_json returns a reference. I am sure this is a

Answer 1

$num_of_hashes = @{$perl_scalar};

Since you're assigning to a scalar, the dereferenced array is evaluated in a scalar context to the number of elements.

If you need to force scalar context then do as KARASZI says and use the scalar function.

Answer 2

You can see the entire structure with Data::Dumper:

use Data::Dumper;
print Dumper $perl_scalar;

Data::Dumper is a standard module that is installed with Perl. For a complete list of all the standard pragmatics and modules, see perldoc perlmodlib.

Answer 3

That would be:

scalar(@{$perl_scalar});

You can get more information from perlreftut.

You can copy your referenced array to a normal one like this:

my @array = @{$perl_scalar};

But before that you should check whether the $perl_scalar is really referencing an array, with ref:

if (ref($perl_scalar) eq "ARRAY") {
  my @array = @{$perl_scalar};
  # ...
}

Update

The length method cannot be used to calculate length of arrays, it's for getting the length of the strings.

Answer 4

You can also use the last index of the array to calculate the number of elements in the array.

my $length = $#{$perl_scalar} + 1;