Re: Proper class setup?

[Chas Owens]

On 6/22/07, Mathew Snyder <[EMAIL PROTECTED]> wrote:
snip

I'm not sure what you mean by "Change your new() in a new() and init()".

snip

What do you mean by "set/get approach"?

snip

Some people believe that new should just create a new blank object and
call an init method to do setup.  There are good arguments both ways.

Manually writing Accessor, Mutator, Getter, or Setter methods sucks
and is error prone.  It is often better to write one getter and one
setter that gets or sets the field(s) passed to it.  Another method is
to use Perl's autoload capability to magically create subroutines for
you.  Starting with some Perl in the 5.8 line the autoload function
gained the ability to be an lvalue, so I have written it that way.

Perl script:
#!/usr/bin/perl

use strict;
use warnings;
use Report;

my $rpt = Report->new;

$rpt->set({id => 5, queue => 10});
print $rpt->printable;

my ($id, $queue) = $rpt->get(qw(id queue));

print "id is $id and queue is $queue\n";

#same thing, but I like the => better
$rpt->set("id", 6);
$rpt->set(id => 6);

print "id is now ", $rpt->get("id"), "\n";

$rpt->id = 7;
print "id is now ", $rpt->id, "\n";

Module:
package Report;

use strict;
use warnings;
use Carp;

our $AUTOLOAD;
our %fields = (
       _id       => 1,
       _queue    => 1,
       _owner    => 1,
       _priority => 1,
       _worked   => 1,
       _timeLeft => 1,
       _due      => 1,
       _created  => 1,
       _updated  => 1,
       _severity => 1,
       _ccl      => 1,
);

#minimal new
sub new {
      my $class = shift;
      my $self  = bless {}, $class;
      $self->init(@_);
      return $self;
}

#real object creation happens here
sub init {
       my $self   = shift;
       my @fields = keys %fields;
       @[EMAIL PROTECTED] = (undef) x @fields;
}

sub _validate_field {
       my ($self, $k) = @_;
       croak "$k is not a valid field for " . ref $self
               unless $fields{"_$k"};
}

#Getter/setter method 1
sub get {
       my ($self, @k) = @_;
       my @ret;
       for my $k (@k) {
               $self->_validate_field($k);
               push @ret, $self->{"_$k"};
       }
       local $" = ' ::: ';
       return @ret
}

sub set {
       my $self = shift;
       croak "bad number of arguments" unless @_ == 2 or @_ == 1;
       if (@_ == 2) {
               $self->_validate_field($_[0]);
               return $self->{"_$_[0]"} = $_[1];
       }
       croak "not a hash reference" unless ref $_[0] eq 'HASH';
       my $h = $_[0];
       my @ret;
       for my $k (keys %$h) {
               $self->_validate_field($k);
               push @ret, $self->{"_$k"} = $h->{$k};
       }
       return @ret;
}

#another form of setter/getter

sub AUTOLOAD : lvalue {
       my ($k) = $AUTOLOAD =~ /::(.*?)$/;
       return if $k eq 'DESTROY';
       my $self = shift;
       $self->_validate_field($k);
       $self->{"_$k"};
}

sub printable {
      my ($self) = @_;

      # return Printable Report info
      return $self->id . " " . $self->queue . "\n";
}

1;

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