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Section 12.3.  Accessing the Instance Data

 
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12.3. Accessing the Instance Data

Because we get the instance as the first parameter, we can now access the instance-specific data. In this case, let's add a way to get at the name:

{ package Horse;
  @ISA = qw(Animal);
  sub sound { 'neigh' }
  sub name {
    my $self = shift;
    $$self;
  }
}

Now we call for the name:

print $tv_horse->name, " says ", $tv_horse->sound, "\n";

Inside Horse::name, the @_ array contains just $tv_horse, which the shift stores into $self. It's traditional to shift the first parameter into a variable named $self for instance methods, so stay with that unless you have strong reasons to do otherwise (Perl places no significance on the name $self, however).[Section 12.3.  Accessing the Instance Data] Then we dereference $self as a scalar reference, yielding Mr. Ed. The result is:

[Section 12.3.  Accessing the Instance Data] If you come from another OO language background, you might choose $this or $me for the variable name, but you'll probably confuse most other Perl OO hackers.

Mr. Ed says neigh.


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