Perl: Searching through hashes

Poetics · 02-26-2009, 06:35 PM

I currently have a data structure that looks as follows (passed from another function, I can't change the structure):

Code:

$employees = {
     'department' = {
          'name' = 'Engineering',
          'employees' = {
               'name' = 'Bob Johnson',
               'id' = '123456889',
               'projects' = { 
                    'id' = '112233',
                    'name' = 'Bob\'s Project 1'
               }
          }
     }
}

and so forth.

If I don't know what department Bob is in, but know his ID #, is it possible for me to retrieve that information? Similarly, if I know a project ID, but not who owns it, can I somehow extrapolate the rest?

I just can't figure out what would go in the

Code:

$employees{__department__}{employees}{__id__}{projects}{id}

designated sections if I were trying to find that information via the project ID.

Thanks much in advance!
-- Christopher

j-ray · 02-27-2009, 03:51 AM

#!/usr/bin/perl

use strict;

my $idGiven = shift;

my ($department, @empkeys, %employees);
%employees = (
'department' => {
'name' => 'Engineering',
'employees' => {
'name' => 'Bob Johnson',
'id' => '123456889',
'projects' => {
'id' => '112233',
'name' => 'Bobs Project 1'
}
}
}
);

foreach $department(keys (%employees)){
if ($idGiven == $employees{'department'}{'employees'}{'id'}){
print "found in department: ".$employees{'department'}{'name'}."\n";
print $employees{'department'}{'employees'}{'name'}."\n";

foreach my $prokey(keys(%{$employees{'department'}{'employees'}{'projects'}})){
print $prokey." -> ".$employees{'department'}{'employees'}{'projects'}{$prokey}."\n";
}
}
}

# watch out plz, I changed the notation of the given hash. The id you are looking for can now be passed as an argument to the script.
the folllowing is another working representation of the hash data:

$employees{'department'} = {
'name' => 'Engineering',
'employees' => {
'name' => 'Bob Johnson',
'id' => '123456889',
'projects' => {
'id' => '112233',
'name' => 'Bobs Project 1'
}
}

};

#so if in perl a scalar vaariable $x contains a hash then it contains a reference to that hash in fact and must be cast to be seen as a hash to the interpreter like %{$x}
Probably this was causing the difficutly?
Hope this helps.

bigearsbilly · 02-27-2009, 04:30 AM

that is a bloody awful way of representing the data structure.
you will have real problems with this unless you clean it up.

should employees and projects be a list? or only one as in the example?
this needs to be properly thought out on your part, (which is fun)
or you'll make life very difficult later on.

anyhow here's a clue...

Code:

#!/usr/bin/perl

use Data::Dumper;
use strict;

our @employees;

my $employee = {
     'department' => {
          'name' => 'Engineering',
          'employees' => {
               'name' => 'Bob Johnson',
               'id' => '123456889',
               'projects' => { 
                    'id' => '112233',
                    'name' => 'Bob\'s Project 1'
               }
          }
     }
};
# make a LIST of employees
# ========================
push @employees, $employee;
#print Dumper @employees;



print "Enter employee ID:";
my $id = <>;
my @L = grep { $_->{department}->{employees}->{id} == $id } @employees;
print Dumper @L;



print "Enter project ID:";
my $id = <>;
my @L = grep { $_->{department}->{employees}->{projects}->{id} == $id } @employees;
print Dumper @L;

Poetics · 02-27-2009, 12:11 PM

The reason the data structure is "set" is that it comes from a module someone else wrote, and my experience with writing my own is very (very) slim; similarly, I have no familiarity with the originating data. A lot of this work would be a prime candidate for simple relational hashes (or even a very basic MySQL db), and some day I'd like to move to that, but for the time being, it's not feasible.

Much obliged for your suggestions though!

Poetics · 02-27-2009, 02:05 PM

I just realized my previous example was faulty (sorry, I tried to simplify and went too far); here's the data set straight from the function:

Code:

{
  $group_id => {
    name => $group_name,
    employees => {
      $emp_id => {
        name => $name,
        location => $location,
        position => $sposition,
        projects => {
          $proj_id => {  
            p_name => $p_name,
            p_due => $p_duedate
          },
        },
      }
    }
  }
}

If I'm provided only with the Project ID, I am trying to find a method through which can extrapolate the employee id and/or group. For example:

Code:

$project1 = $var->{'12345'}{'employees'}{'98765'}{'projects'}{'6543'}{'p_name'};

is just fine, if I have all of the relevant data. But what if I had only "6543" as the project ID, and lacked the group_id and emp_id variables?