Hello Perl Object World

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Creating your own Classes example from a Well House Consultants training course
More on Creating your own Classes [link]

This example is described in the following article(s):
• Teaching examples in Perl - third and final part - [link]

Source code: at2 Module: P213

=head1

This is a short Perl program showing both the setting
up and use of Objects in a Perl program. Compare to
out antest example, which shows the background to how
this works via Perl packages without the true OO aspects.

Note that when you bless a pointer to a variable, you'll
get a scalar back that includes:
a) The address of the object
b) The type of object
c) The internal data type (SCALAR, HASH or ARRAY) used

The scalar returned by bless (and returned by the new sub
too, as it's the last expression evaluated in the sub) can
then be passed in to the subs that provide functionallity -
that's vpk in our example - and if that's done using the ->
notation, you can get Perl to select which vpk it is -
potentially from many subs of the same name - based on the
type of data that the scalar points to.

=cut

{
package animal;

sub new{
        ($class,$name,$we,$val) = @_;
        my %info;
        $info{name} = $name;
        $info{weight} = $we;
        $info{value} = $val;
        bless \%info,$class;
        }
sub vpk{
        ($current) = @_;
        return $$current{value} / $$current{weight};
        }

}

$gyp = new animal("Gypsy",28,200);
$cha = new animal("Charlie",3,250);

$g_vpk = $gyp->vpk();
$c_vpk = $cha->vpk();

print ("$gyp $cha\n");
print ("values are $g_vpk and $c_vpk\n");

__END__

Sample output:

Dorothy-2:j10p grahamellis$ perl at2
animal=HASH(0x801a30) animal=HASH(0x801cc4)
values are 7.14285714285714 and 83.3333333333333
Dorothy-2:j10p grahamellis$

Learn about this subject

This module and example are covered on the following public courses:
* Perl Programming
* Perl for Larger Projects
* Learning to program in Perl
* Perl Programming
Also available on on site courses for larger groups

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Other Examples

This example comes from our "Creating your own Classes" training module. You'll find a description of the topic and some other closely related examples on the "Creating your own Classes" module index page.

Full description of the source code

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Further Examples

3cl - Object Orientation - 2 classes and polymorphism

antest - Introduction to Objects

at2 - Hello Perl Object World

bd1.pm - A simple class, using a scalar to store object information

bd2.pm - A simple class, using a list to store information about each object

bd3.pm - A simple class, storing each object in a hash

big - How Object Inheritance is done in Perl

blessing - Blessing and resultant polymorphism

book.pm - A simple class with a constructor and 2 access methods

ce.pm - Object interface to call events