weezer_316 has asked for the wisdom of the Perl Monks concerning the following question:

Hi

I am having some trouble with hashes with a package I am writing for my company which deals with dental patients.

Basically, I have code like the sample below with patients details,thing like name, address, dob etc in the an array of hashes

Now, what I want to do is loop through each patient in turn and add the patient to a new hash key'd on thier dentists surgery ID. 

$practice = {}; 

foreach $patient(@{$self->{patient_details}})
{
     $practice->{$patient->{suregery_id}} = \$patient;
}

[download]

In theory, I should group all the patients with a surgery ID of 1, 2, 3 etc togther. However it isnt working. I have tried puting them in arrays, new hashes, sub routines passing back a hash, but i still cant get them all groupped together

Any ideas how I could do it?

Replies are listed 'Best First'.
Re: In a hash with hashes
by BrowserUk (Patriarch) on Jan 10, 2010 at 13:23 UTC

    You're overwriting the hash value with each new patient. Try: 

    $practice = {}; 

foreach $patient(@{$self->{patient_details}})
{
     push @{ $practice->{ $patient->{suregery_id} } }, $patient;
}

    [download]

    It creates an array of patients for each id.

    Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
    "Science is about questioning the status quo. Questioning authority".
    In the absence of evidence, opinion is indistinguishable from prejudice.
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[d/l]

      Since BrowserUk has already provided the answer, this reply is very much BTW, but FWIW...

      In the OPed code fragment, the statement
          $practice->{$patient->{suregery_id}} = \$patient;
      repeatedly assigns (i.e., overwrites) a reference to  $patient to the hash key  $patient->{suregery_id} of the hash referenced by  $practice.

      The OPed code iterates over an array of hash references, so  $patient is already a hash reference. The statement above repeatedly assigns the LHS hash element a reference to a reference to a hash, which is probably even less what weezer_316 wanted! (Again, not that it matters much at this point.)

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[d/l]
[select]

      The code is at work, I'm at home, but I think your a genius! Thats utterly obvious and ive totally missed it. Thanks alot!

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Re: In a hash with hashes
by apl (Monsignor) on Jan 10, 2010 at 13:36 UTC
    Are you certain you want the hash based on suregery_id, or do you mean $suregery_id?
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[d/l]
[select]

      SugeryID. The data is being pulled from a database and the rows title is SurgeryID so ill keep it as it is.

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