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

I am trying to construct a moose class that represents a single record retrieved from the db. I'm getting a problem which I'm pretty sure is from the attempt to assign values to a hash "property" of the class. But I could be wrong ;o) 

package AXRecord;

# Our libraries
use lib 'C:\Users\Jay\Desktop\SBS DEV\CODE\perl\Utilities';
use AXControl;
use AXSQL;


use Moose;
use DBI;

# Attributes
has 'Name' => (is => 'rw', isa => 'Str', required => 1);
has 'Fields' => (is => 'ro', isa => 'Hash');
has 'FieldCount' => (is => 'ro', isa => 'Num');
has 'Changed'  => (is=>'rw', isa => 'Boolean');
has 'Where' => (is => 'rw', isa => 'Str'); 
has 'ControlObject' => (is => 'rw', isa => 'Object', required => 1);
has 'Keys' => (is => 'rw', isa=>'Array');
# Contains a single record

sub BUILD
# Constructor
{
    my $self;    
    $self = shift;
    
    if (defined $self->Where)
        {
        $self->Select();
        }
}
# Insert the record
sub Insert
{

}
#Delete using the keys in the record
sub Delete 
{


}
#Update using the keys and values in the record
sub Update
{



}
#Save the record
sub Save
{


}

sub Select
{
    my ($SQLStr, $Cnt, $sql, @Values, $self, $Col, @Flds, $i);
    
    $self = shift;
    
    $SQLStr = "SELECT * FROM " . $self->Name . ' ' . $self->Where;
    $sql = AXSQL->new(ControlObject => $self->ControlObject, SQLString
+ => $SQLStr);
    
    #construct a hash using the metadata and the data from the actual 
+table
    $self->Fields = {};
    @Values = $sql->Fetch();
    #Get field Names
    $sql = AXSQL->new(ControlObject => $self->ControlObject, SQLString
+ => "show fields from '" . $self->Name . "'");
    @Flds = $sql->fetch();
    # Construct the hash
    for ($i..$#Flds)
        {
        $self->Fields{$Flds[$i]} = $Values[$i];
        }
    
    $self->Keys = ();
    $sql = AXSQL->new(ControlObject => $self->ControlObject, SQLString
+ => "SELECT column_name FROM information_schema.`key_column_usage` WH
+ERE table_name = '" . $self->name . "' order by ordinal_position");
    while (($Col) = $sql.fetch())
        {
        push $self->Keys, $Col;
        }
    
    $Cnt = $self->Fields;
    $self->FieldCount = $Cnt;
    $self->Changed = -1;

}

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The error messages I am getting all seem to be caused by what I'm doing wrong in this statement 

$self->Fields{$Flds[$i]} = $Values[$i];

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All of the declaration errors are about variables that work fine before that line. The hash Fields is a property of the class and I'm trying to populate it with fieldname/value pairs Here are the error messages (moose warnings excluded) 

C:\Users\Jay\Desktop\SBS DEV\CODE\perl\Utilities>perl -w AXRecord.pm

push on reference is experimental at AXRecord.pm line 83.
syntax error at AXRecord.pm line 76, near "->Fields{"
Global symbol "$self" requires explicit package name (did you forget t
+o declare
"my $self"?) at AXRecord.pm line 79.
Global symbol "$sql" requires explicit package name (did you forget to
+ declare "
my $sql"?) at AXRecord.pm line 80.
Global symbol "$self" requires explicit package name (did you forget t
+o declare
"my $self"?) at AXRecord.pm line 80.
Global symbol "$self" requires explicit package name (did you forget t
+o declare
"my $self"?) at AXRecord.pm line 80.
Global symbol "$Col" requires explicit package name (did you forget to
+ declare "
my $Col"?) at AXRecord.pm line 81.
Global symbol "$sql" requires explicit package name (did you forget to
+ declare "
my $sql"?) at AXRecord.pm line 81.
Global symbol "$self" requires explicit package name (did you forget t
+o declare
"my $self"?) at AXRecord.pm line 83.
Global symbol "$Col" requires explicit package name (did you forget to
+ declare "
my $Col"?) at AXRecord.pm line 83.
Global symbol "$Cnt" requires explicit package name (did you forget to
+ declare "
my $Cnt"?) at AXRecord.pm line 86.
Global symbol "$self" requires explicit package name (did you forget t
+o declare
"my $self"?) at AXRecord.pm line 86.
Global symbol "$self" requires explicit package name (did you forget t
+o declare
"my $self"?) at AXRecord.pm line 87.
Global symbol "$Cnt" requires explicit package name (did you forget to
+ declare "
my $Cnt"?) at AXRecord.pm line 87.
Global symbol "$self" requires explicit package name (did you forget t
+o declare
"my $self"?) at AXRecord.pm line 88.
syntax error at AXRecord.pm line 90, near "}"
AXRecord.pm has too many errors.

C:\Users\Jay\Desktop\SBS DEV\CODE\perl\Utilities>

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Replies are listed 'Best First'.
Re: Invalid Reference Use - warning Noob
by choroba (Cardinal) on Oct 15, 2017 at 19:16 UTC
    Fields is an accessor, i.e. a method. You can't treat a method call as a hash. But the method returns a hash reference, so you can dereference it: 
    #!/usr/bin/perl
use warnings;
use strict;

{
    package MyStruct;
    use Moose;

    has fields => ( is => 'rw' );

    __PACKAGE__->meta->make_immutable;
}

my $s = 'MyStruct'->new(fields => { a => 0, b => 1 });
$s->fields->{b}++;
print $s->fields->{b};

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    Update: Another option is to use traits: 

    #!/usr/bin/perl
use warnings;
use strict;

{
    package MyStruct;
    use Moose;

    has fields => ( is => 'rw',
                    isa => 'HashRef',
                    traits => ['Hash'],
                    handles => {
                        set_fields => 'set',
                        get_fields => 'get',
                    },
                  );

    __PACKAGE__->meta->make_immutable;
}

my $s = 'MyStruct'->new(fields => { a => 0, b => 1 });
$s->set_fields(b => $s->get_fields('b') + 1);
print $s->get_fields('b');

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    ($q=q:Sq=~/;[c](.)(.)/;chr(-||-|5+lengthSq)`"S|oS2"`map{chr |+ord
}map{substrSq`S_+|`|}3E|-|`7**2-3:)=~y+S|`+$1,++print+eval$q,q,a,

    [download]
[reply]
[d/l]
[select]
      That has solved the problem. many thanx J.
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Re: Invalid Reference Use - warning Noob
by Corion (Patriarch) on Oct 15, 2017 at 19:13 UTC

    Did you maybe mean to access the hash reference?

    $self->Fields->{ ... }

    [download]
[reply]
[d/l]
Re: Invalid Reference Use - warning Noob
by Mr. Muskrat (Canon) on Oct 16, 2017 at 18:16 UTC

    It looks like you are trying to write your own object-relational mapping (ORM) tool. Do yourself (and your employer) a favor and check out DBIx::Class before you go any further down that rabbit hole. (The Grue dwells in the darkness.)

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