in reply to OOP - Sharing class methods

Why not make both class1 and class2 inherit from a base class which implements the common code?

-pete
"Pain heals. Chicks dig scars. Glory lasts forever."

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Re: Re: OOP - Sharing class methods
by perrin (Chancellor) on Aug 14, 2002 at 18:52 UTC
    Inheritance is one way to go, but it should only be used when there is a clear inheritance relationship between the objects being modeled. A more common solution would be to just put the shared code in a separate utility class and have the other classes use that.
[reply]
      How you make use of your utility class is somewhat interesting though. The naïve approach can lead to problems down the road when you make a subclass and it needs to have a slightly different version of some or all of the methods provided by the utility class.

      Here's a naïve implementation: 

      package Foo;
use UtilityClass;

sub some_method {
    my $self = shift;
    $self->UtilityClass::some_method(@_);
}

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      Nothing wrong with that, is there? Well... yes, because stuff is hardcoded, you may find that, when you come to subclass foo, things will break. A better approach is: 
      package Foo;
use UtilityClass;

sub helper_class { 'UtilityClass' };

sub some_method {
    goto &{ $_[0]->helper_class->can('some_method') };
}

      [download]
      You could go further and add per object customization, by turning 'helper_class' into an instance method, allowing you to choose which utility class to use on an object by object basis rather than class by class...
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        I didn't see any mention of proxying methods off to this other class. I interpreted the question as one of how to share some common functionality, not how to pass method calls off to a different class.

        Since we're doing OO and therefore concerned about inheritance and such, the utility class should be an actual class and use class methods: 

        package Foo;
use UtilityClass;

sub bubbles {
    ...class-specific stuff...
    UtilityClass->buttercup();
    ...class-specific stuff...
}

        [download]
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