Intermediate Perl Learning Notes --chapter 11

Personal Answers to Exercises 1 & 2:

LivingCreature.pm:

#! /usr/bin/perl -w
use strict;

package LivingCreature;

sub speak()
{
    my $class = shift;
  if (@_ == 0)
  {
      print STDOUT "Here goes $class ",$class->sound,"!\n";
  }
  else
  {
      print STDOUT "Here goes $class ",$class->talk(@_),"!\n";
  }
}

1;

 Animal.pm:

#! /usr/bin/perl -w
use strict;
require 'LivingCreature.pm';

package Animal;
our @ISA = qw(LivingCreature);
sub speak
{
    my $class = shift;
    print STDOUT "A $class goes ",$class->sound,"!\n";
}

1;

Person.pm:

#! /usr/bin/perl -w
use strict;
require 'LivingCreature.pm';

package Person;
our @ISA = qw(LivingCreature);

sub sound()
{
    'Humming';
}

sub talk()
{
    shift;
    "@_";
}

sub speak()
{
    my $class = shift;
  $class->SUPER::speak(@_);
}

1;

Cow.pm:

#! /usr/bin/perl -w
use strict;
require 'Animal.pm';
package Cow;

our @ISA = qw(Animal);

sub sound
{
    'moooo';
}

sub speak
{
    my $class = shift;
    $class->SUPER::speak(@_);
}

1;

Horse.pm:

#! /usr/bin/perl -w

use strict;
require 'Animal.pm';

package Horse;

our @ISA = qw(Animal);

sub sound()
{
    'neigh';
}

sub speak()
{
    my $class = shift;
    $class->SUPER::speak(@_);
}

1;

Sheep.pm:

#! /usr/bin/perl -w
use strict;
require 'Animal.pm';

package Sheep;
our @ISA = qw(Animal);

sub sound()
{
    'baaaah';
}

sub speak()
{
    my $class = shift;
    $class->SUPER::speak(@_);
}

1;

AnimalMain.pl

 

#! /usr/bin/perl -w
use strict;

require 'Cow.pm';
require 'Horse.pm';
require 'Sheep.pm';
require 'Person.pm';

chomp(my $line = <>);
my @pasture = split(/\s+/,$line);
foreach my $animal(@pasture)
{
    next if ( $animal ne 'Cow' && $animal ne 'Horse' && $animal ne 'Sheep' );
    $animal->speak;
}

Person->speak("Hi,songwolf");
Person->speak;

 

总结:

1.our变量修饰符的使用

2.抽象公共行为成为基类的公共函数,回调子类的方法产生个性化行为.