Accessing nested JSON elements in Perl - json

Question

I get an error when attempting to access the contents of my JSON array.
Here is the contents of my JSON array assets.json:
[{"id":1002,"interfaces":[{"ip_addresses":[{"value":"172.16.77.239"}]}]},{"id":1003,"interfaces":[{"ip_addresses":[{"value":"192.168.0.2"}]}]}]
Here is my code
#!/usr/bin/perl
use strict;
use warnings;
use JSON::XS;
use File::Slurp;
my $json_source = "assets.json";
my $json = read_file( $json_source ) ;
my $json_array = decode_json $json;
foreach my $item( #$json_array ) {
print $item->{id};
print "\n";
print $item->{interfaces}->{ip_addresses}->{value};
print "\n\n";
}
I get the expected output for $item->{id} but when accessing the nested element
I get the error "Not a HASH reference"

Answer 1

Data::Dumper is your friend here:
Trying this:
#!/usr/bin/env perl
use strict;
use warnings;
use JSON::XS;
use Data::Dumper;
$Data::Dumper::Indent = 1;
$Data::Dumper::Terse = 1;
my $json_array = decode_json ( do { local $/; <DATA> } );
print Dumper $json_array;
__DATA__
[{"id":1002,"interfaces":[{"ip_addresses":[{"value":"172.16.77.239"}]}]},{"id":1003,"interfaces":[{"ip_addresses":[{"value":"192.168.0.2"}]}]}]
Gives:
[
{
'interfaces' => [
{
'ip_addresses' => [
{
'value' => '172.16.77.239'
}
]
}
],
'id' => 1002
},
{
'interfaces' => [
{
'ip_addresses' => [
{
'value' => '192.168.0.2'
}
]
}
],
'id' => 1003
}
]
Important point of note - you have nested arrays (the [] denotes array, the {} a hash).
So you can extract your thing with:
print $item->{interfaces}->[0]->{ip_addresses}->[0]->{value};
Or as friedo notes:
Note that you may omit the -> operator after the first one, so $item->{interfaces}[0]{ip_addresses}[0]{value} will also work.