Create small simple OO program with get/set, defaults, initialization

Create a Object oriented perl class quickly and easily, including get and set and clear methods, with a default values hash and an initialization hash. Object Oriented Perl by Damian Conway section 8.2 (pages 222-235) has a good treatment of this, but doesn't provide workable code. Below is the code to do this.

package Simple;
use Class::MethodMaker
  get_set => [qw(a b)],
  new_with_init => 'new';
sub init  {
  my $self         = shift;
  my %in_args      = @_;
  my %default_args = ( b => "default");
  my %final_args   = (%default_args, %in_args);
  foreach my $thiskey (keys(%final_args)) {
    $self->{$thiskey} = $final_args{$thiskey};
  }
  return;
}
-------------- in use_it.pl ---------
use Simple;
my $test = new Simple (a=>1);
# now a==1, b==default.
my $test = new Simple (a=>1, b=>2);
# now a==1, b==2.
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Re: Create small simple OO program with get/set, defaults, initialization by rob_au (Abbot) on Jul 03, 2002 at 06:24 UTC
Another way to do it ... `package Simple; use Class::MethodMaker get_set => [ qw/ a b / ], new_with_init => 'new'; sub init { my ($class, %args) = @_; my %default = ( 'b' => 'default' ); %args = (%args, %default); bless \%args, $class; }` [download] The difference here is that the arguments hash, `%args`, is blessed as an object rather than singularly creating each element as was being performed. Also too, this approach lends itself well to argument validation, for example with the addition of a single validation loop: `use Carp; %args = (%args, %default); foreach (keys %args) { carp( 'Unknown argument to init subroutine - ', $_ ) unless exists + $default{$_}; } bless \%args, $class;` [download] This approach allows for the keys in the passed `%args` hash to be validated against the `%default` hash so that only allowed elements are included in the object.	[reply] [d/l] [select]

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Re: Create small simple OO program with get/set, defaults, initialization
by rob_au (Abbot) on Jul 03, 2002 at 06:24 UTC

package Simple;

use Class::MethodMaker
    get_set         =>  [ qw/ a b / ],
    new_with_init   =>  'new';

sub init {
    my ($class, %args) = @_;

    my %default = (
        'b' =>  'default'
    );

    %args = (%args, %default);
    bless \%args, $class;
}
[download]

The difference here is that the arguments hash, %args, is blessed as an object rather than singularly creating each element as was being performed. Also too, this approach lends itself well to argument validation, for example with the addition of a single validation loop:

use Carp;

%args = (%args, %default);
foreach (keys %args) {
    carp( 'Unknown argument to init subroutine - ', $_ ) unless exists
+ $default{$_};
}
bless \%args, $class;
[download]

This approach allows for the keys in the passed %args hash to be validated against the %default hash so that only allowed elements are included in the object.

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