sanjeevbinf has asked for the wisdom of the Perl Monks concerning the following question:

dear forum members,

my query must be a silly, but I have been finding hard to undestand json. Apart from knowing it is a key value pair, I cannot undertand much. How to initiate it. How to loop over it. How to print it without using print Dumper. Is it a hash or is it reference?

example: 
my $son = '{        
}';
my $r=decode_json($son);#cannot understand why I need to do


$r->{"trans2"}[0]="90";
$r->{"trans2"}[1]="20";
print "\n\n";

#print Dumper \$r; # without dumper, how can I iterate using for loop?

print $r->{"trans2"}[0],"\n"; #hard coded
print $r->{"trans2"}[1],"\n"; #hard coded

[download]
Above, I want 2 values in trans1 key.

How do I iterate over keys in json object?

Sorry, I have posted this in wrong forum. Admins, pleae move this thread to respective forum

Replies are listed 'Best First'.
Re: understanding json in perl
by atcroft (Abbot) on Apr 25, 2014 at 04:43 UTC

    Looking at your code, first of all you only need the decode_json() statement if you have a value provided to you in JSON format. If not, then you can start with a familiar perl data structure, and use the encode_json() statement to convert it to something to be passed elsewhere. Here is a short example:

    Read more... (1162 Bytes)

    Hope that helps.

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[d/l]
      @atcroft Thank you for you the code. I needed the output like the encode one. Now I get the hold of it. Shall work on it.

      @ NetWallah , sundialsvc4- Thank you for the replies.

[reply]
Re: understanding json in perl
by NetWallah (Canon) on Apr 25, 2014 at 05:35 UTC 
    use strict;
use warnings;
use Data::Dumper;
use JSON;

my $son = '{    
     "trans2": [   90, 20 , 80, 33 ]
}';  # THIS IS a *STRING* 

my $r=decode_json($son);#cannot understand why I need to do
  # the 'decode' converts the string into a  a perl structure (Hash re
+f), and store in $r
print Dumper \$r; # without dumper, how can I iterate using for loop?
# Here's how to iterate ..
for my $k (sort keys %$r){
  print "Values under $k:\n";
  for my $val (@{$r->{$k}}){
     print "$val, ";
  }
  print "\n";
}

    [download]
    Output: 
    $VAR1 = \{
            'trans2' => [
                          90,
                          20,
                          80,
                          33
                        ]
          };
Values under trans2:
90, 20, 80, 33,

    [download]

            What is the sound of Perl? Is it not the sound of a wall that people have stopped banging their heads against?
                  -Larry Wall, 1992

[reply]
[d/l]
[select]
Re: understanding json in perl
by locked_user sundialsvc4 (Abbot) on Apr 27, 2014 at 00:29 UTC

    JSON is, of course, merely a data-format.   In much younger and more innocent days, it was favored because it basically is JavaScript, and sites could (and did!) merely exec it.   Today, you use a CPAN module such as JSON (as previously shown) both to encode and to decode the data.   (Safely.)   What you get is a Perl data structure, namely a hash.

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