Searching in a JSON array with Perl - arrays

Question

I need to search for a specific term in a JSON array and get the index of the array element which contains the term as its value of a key, below is a sample JSON file that I'm working on, I need to get the array element whose "artifact_id" is "jar", so in this case I need to get the index of the array which is 1, the "artifact_id" is guaranteed to be unique:
{
"maven": [
{
"version": "1.2",
"artifact_id": "zip"
},
{
"version": "1.2",
"artifact_id": "jar"
}
]
}
I'm using the JSON lib and can decode the JSON to a Perl object, anyone can suggest the next step for me? Thanks a lot.
my $json_text = do {
open( my $json_fh, "<:encoding(UTF-8)", $filename[0] )
or die("Can't open \$filename\": $!\n");
local $/;
<$json_fh>;
};
my $json = JSON->new;
my $json_data = $json->decode($json_text);

Answer 1

Simply iterate through your array, and store away the index once the matching node is found. The example below should speak for itself, but given the contents of your post I guess you should read up on loops, comparitive operators, as well as basic programming.
After you have decoded your JSON-data, there is nothing special about iterating over the array, after all; it is just an array (reference given the tree like structure of JSON).
use JSON qw(decode_json);
my $needle = "jar";
my $needle_location;
my $data = decode_json( join '', <DATA> );
while( my( $idx, $elem ) = each( #{$data->{'maven'}} ) )
{
if( $elem->{'artifact_id'} eq $needle )
{
$needle_location = $idx;
last;
}
}
die "unable to find entry" unless defined $needle_location;
print "needle_location: $needle_location\n";
__DATA__
{
"maven": [
{
"version": "1.2",
"artifact_id": "zip"
},
{
"version": "1.2",
"artifact_id": "jar"
}
]
}
needle_location: 1

Answer 2

My answer is based on that of Filip Roséen - refp, but hopefully a more advanced and abbreviated approach:
use Modern::Perl;
use List::Util qw(first);
use JSON qw(decode_json);
my $needle = "jar";
my $data = decode_json do { local $/; <DATA> };
my $needle_location = first( sub {
my $artifact_id = $data->{ maven }->[ $_ ]->{ artifact_id };
defined($artifact_id) && $artifact_id eq $needle
}, 0 .. $#{ $data->{ maven } } ) //
die "unable to find entry";
say "needle_location: $needle_location";
__DATA__
{
"maven": [
{
"version": "1.2",
"artifact_id": "zip"
},
{
"version": "1.2",
"artifact_id": "jar"
}
]
}