Return a hash value based on its key

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

Hi Monks!
I looking into returning a message based on a passed key value from a sub. I am getting a number 10 from the check sub instead of the message I am looking for. How can I do this thing right?
Here is sample code I am trying:

#!/usr/bin/perl

use strict;
use warnings;

use Data::Dump 'pp';
use Text::CSV;

main();


sub main {

 my $data = shift || return;
 my $file = "file.txt";
 
 eval {
     
   open my $fh, ">", $file or die "Unable to create or open file: $!";

     $csv->print($fh, $_) for @{ $data };

   close $fh; 
 };
 
  if ($@) {
  
    print "ERROR!";
    
  }else {

    # A message code will be here, using 1114 as sample;
    my $message = check('1114');
    print $message;

    # I want to print " Exit " <<<<<<<<<<<

  };
  

} 

sub check {

 my $ck = shift;

 my %message= (
 
    'y345'   => " Close ",
    '1223dx' => " Open ",
    '88888'  => " Gone ",
    'acb2'   => " Available ", 
    '1114'   => " Exit ",
    
  );

}
[download]

Thanks for the help!

Comment on Return a hash value based on its key Download Code

Replies are listed 'Best First'.
Re: Return a hash value based on its key by kennethk (Abbot) on Feb 16, 2016 at 19:38 UTC
The difficulty you are having is because `check` returns the ten element list of key-value pairs, not the value associated with the passed key. You'll get your expected result if you include the explicit return statement `return $message{$ck};` as the last line of your sub. As a side note, you should make sure that code you post passes `perl -c` (compiles). Yours does not because you didn't include a line like: `my $csv = Text::CSV->new;` [download] #11929 First ask yourself `How would I do this without a computer?' Then have the computer do it the same way.	[reply] [d/l] [select]
Re^2: Return a hash value based on its key by Anonymous Monk on Feb 16, 2016 at 19:52 UTC
You're right, thanks for helping!	[reply]
Re: Return a hash value based on its key by AnomalousMonk (Archbishop) on Feb 16, 2016 at 21:43 UTC
In addition to kennethk's comment above, I would also recommend that you add a validity check to `check()`, something like (untested): `sub check { my $ck = shift; my %message= ( 'y345' => " Close ", '1223dx' => " Open ", '88888' => " Gone ", 'acb2' => " Available ", '1114' => " Exit ", ); return 'unknown or missing check value' unless defined($ck) and exists $message{$ck}; return $message{$ck}; }` [download] (Instead of returning an oddball message, you could die at that point.) Also note that in the OPed code, `main()` is called without arguments. As such, in the statement `my $data = shift \|\| return;` the value returned by shift will always be undefined, hence false, and `main()` will always immediately return. Give a man a fish: `<%-{-{-{-<`	[reply] [d/l] [select]