(tye)Re: how do I do multiple inheritance

I'd like to mention that this is a classic example of how inheritance is taught in OO text books and is also a classic example of how to not use inheritance in the real world.

I wish I could eloquently explain why this is such a bad idea. The basic problem is that inheritance is a very tight binding between types and it can easily tie you up down the road and make things very difficult. You are usually better off having one object contain a reference to another over having the one inherit from the other.

- tye (but my friends call me "Tye")

Comment on (tye)Re: how do I do multiple inheritance

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Re: (tye)Re: how do I do multiple inheritance by herveus (Prior) on Jan 26, 2002 at 01:53 UTC
Howdy! I'll take a whack at it... If you say `package Employee; use Person; use Gender; @ISA = qw/Person Gender/;` [download] you are saying that an Employee is both a Person and a Gender. You probably want something where Gender is an attribute of Person or Employee. Something like: `package Person; use Gender; sub new { ... $self->{gender} = Gender->new; ... }` [download] Now, Persons have among their attributes a Gender. But a Person is not a Gender. HAS-A versus IS-A. yours, Michael	[reply] [d/l] [select]

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Re: (tye)Re: how do I do multiple inheritance
by herveus (Prior) on Jan 26, 2002 at 01:53 UTC

I'll take a whack at it...

If you say

package Employee;
use Person;
use Gender;
@ISA = qw/Person Gender/;
[download]

You probably want something where Gender is an attribute of Person or Employee. Something like:

package Person;
use Gender;

sub new
{
   ...
   $self->{gender} = Gender->new;
   ...
}
[download]

Now, Persons have among their attributes a Gender. But a Person is not a Gender. HAS-A versus IS-A.

yours,
Michael

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