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All the Perl that's Practical to Extract and Report

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  • Not completely into Moose yet, but isn't a role the equivalent of a Java interface?

    In that case, the behaviour you describe has been implemented there as a intended feature: a regular class *implements* the interface.

    Additionally, a role seems to also have the function of an abstract class as well. In Java, overriding concrete methods is, again, a feature you want.

    If you don't want to override a method simply do not include a overloading method in the implementing class.

    It looks like a (sensible) design dec

    • Roles are far more than interfaces. I strongly recommend reading up on them to understand what they do. The protect (usually) against method collision and they provide a default implementation. If you want to use one like an interface, it's simple:

      package MyRole::DoesSomething;

      use Moose::Role;
      requires qw(
          save
          search
      );

      And now your classes (or some other role composed into said classes) must provide save and search methods.

      However, if you have this:

      package MyRole::DoesSomethi

      • So it's indeed also like an Abstract class in Java. The solution for the problem in the Java world is the @Override annotation before the overriding method.

        It overrides silently, but it's clear in your code and your IDE will warn you if you don't add the @Override annotation.

        Something like that would indeed save debugging time.

        C.

        • So it's indeed also like an Abstract class in Java.

          A role is like an abstract class in Java in the same way lightning is like a lightning bug.

        • No, it's not like an abstract class. I can compose several roles into my class in Perl, but I can't multiply inherit from several abstract classes in Java. Further, if I have two roles which provide the same method name, this fails at composition time but roles (particularly with Moose) offer you a rich variety of ways of resolving conflicts. You don't get that benefit with abstract classes.

          You also mention the silent overriding and the "clear in your code" and "your IDE will warn you". Two problems wit

          • I see your point about multiple inheritance.

            However, annotations are a language feature and not something IDE-centric.

            • Ah, my apologies about misunderstanding the annotations. It's been too long since I've programmed Java (er, or something like that :)