Hello dvinay,

Of course it’s possible! What happened when you tried it?

But, just because something is possible, that doesn’t mean it is a good idea. And in this case, it’s not, because it undermines the whole point of inheritance. By making Employee inherit from Person, you are saying that an Employee ISA Person; or, in other words, that everything that is true of a Person is also true of an Employee. In particular, this means that you can call the getFirstName method on an Employee and expect to get back the first name of a Person.

One place this comes into its own is when you have other subclasses of Person — say, Manager and Customer — and you want to process them all together in a Person array:

my @People;
...
push @People, Employee->new(...);
...
push @People, Customer->new(...);
...
push @People, Manager->new(...);
...
# etc.
...
for my $person (@People)
{
    ...
    print $person->getFirstName;
    ...
}

[download]

(This is called polymorphism.) There is nothing wrong with overriding an inherited method — that’s a major feature of the whole OO paradigm — but changing the method’s signature or return type undermines polymorphism and so negates one of the main values of using inheritance.

You don’t say why you want to do this, but whatever the reason, it’s almost certainly a symptom of a faulty OO design.

Hope that helps,

Athanasius <°(((>< contra mundum Iustus alius egestas vitae, eros Piratica,

In reply to Re^3: Changing signature of overridden method by Athanasius
in thread Changing Signature of overrided methods by dvinay

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