creating a subroutine in Perl that will take a hash from a hash of hashes as an argument and print out one of the values from that hash

Question

More details:

1st hash: hash of error messages
2nd hash: error message itself (error_name)

which contains 3 key values (statusCode, message, params)

I am trying to create a method that will take in error_name and print out the message. This is the code I have at the minute:

`our %error = (
               ERROR_1 => {
                                     statusCode => 561.
                                     message => "an unexpected error occurred at location X",
                                     params => $param_1,
                          }
               ERROR_2 => {
                                     statusCode => 561.
                                     message => "an unexpected error occurred at location Y",
                                     params => $param_1,
                          }
);
`

Is this possible? I'm trying to create a subroutine that will take an error from the hash %error and print out its message. Is this possible? Or maybe there is a better way of doing it.

Short answer: Yes. But you will get more detailed answers if you'd show us a short example (perl code) of how your structure looks like. — PerlDuck, Mar 03 '16 at 20:37
You should post the code you're having a problem with. See [ask] for more information. — Matt Jacob, Mar 03 '16 at 21:05

Eugen Konkov · Accepted Answer · 2016-03-05T13:35:00.703

Some examples to understand structures. These all mean same (with small difference):

# just a hash
%hash = ( 'a', 1, 'b', '2' );
%hash = ( a => 1, b => '2' );
# ref to hash
$hash_ref = \%hash;
$hash_ref = { a => 1, b => 2 };

print $hash{ a }; #prints 1
print $hash_ref->{ a }; #prints 1

1 and '2' are values. Values maybe only scalars. Reference to SOMETHING is also scalar. $hash_ref in the example above.

In your example you say 1st hash is list. I think you mean array:

$list = [ $error1, $error2 ];

$error1 = { error_name => $description }

$description = { status => 'status', message => 'msg', params => [ 1,2,'asdf'] }

You know that a sub get list of scalars. If you want to pass hash into sub you just pass reference to this hash

fn( \%hash );

and get this hash at sub:

sub fn { 
    my( $hash ) =  @_;
    print $hash->{ key_name };
}

I suppose you have just a list of errors, each of them contain keys:

$list_of_errors = [
    { status => 1, message => 'hello' },
    { status => 2, message => 'hello2' },
    { status => 1, message => 'hello3' },
] 

fn( $list_of_errors );

sub fn {
   my( $le ) =  @_;

   print $le->[1]{ message }; #will print 'hello2'
   # print $le->{ error_name }{ status }; #try this in case hash of hashes
}

To understand structures better try to use Data::Dump module;

use Data::Dump qw/ pp /;
%hash = ( a => 1 );
$hash = \%hash;
$arr =  [ 1, 2, 'a' ];
print pp $hash, \%hash, $arr;

Good luck.

CODE

our %error = (
    ERROR_1 => {
         statusCode => 561,
         message => "an unexpected error occurred at location X",
         params => $param_1,
    },
    ERROR_2 => {
         statusCode => 561,
         message => "an unexpected error occurred at location Y",
         params => $param_1,
   }
);

sub print_err {
    my( $err_name ) =  @_;

    print $error{ $err_name }{ message } ."\n";
}

print_err( 'ERROR_1' );
print_err( 'ERROR_2' );

creating a subroutine in Perl that will take a hash from a hash of hashes as an argument and print out one of the values from that hash

1 Answers1