use Perl

• I don't get it (Score:1)

  by hex (3272)

  # Hello Demeter!  (Yeah, this is contrived)
  my $office = $cust->salesman->manager->office;

  What's wrong with this?
  • Re:I don't get it (Score:2)

    by Ovid (2709) on 2007.09.27 5:37 (#58071) Homepage Journal

    my $office = $cust->salesman->manager->office;

    It's a question of encapsulation. Imagine that the Salesman class no longer has need of a manager accessor, but you still need to know which office the salesman is with. You might get a office method pushed into the Salesman class. Then, every place where you have the above code needs to be changed to:

    my $office = $cust->salesman->office;

    If that's called a lot, it can be a maintenance nightmare.

    However, what if you have this?

    sub Customer::office { shift->salesman->manager->office }

    Then, your calling code (again, remember this example is contrived), becomes this:

    my $office = $cust->office;

    At this point, if you need to change the hierarchy, you only have to alter &Customer::office instead of all of the calling code. You've properly encapsulated the hierarchical structure and greatly improved maintainability.

    Reply to This

    Parent

    • Re: (Score:1)

      by hex (3272)

      You've properly encapsulated the hierarchical structure and greatly improved maintainability. Oh, I see what you mean now. Right, thanks.
      • Re: (Score:2)

        by Ovid (2709)

        You're welcome. It's not exactly intuitive. Took me a couple of tries to get it :)
    • Re: (Score:1)

      by perigrin (3495)

      Thank you. I hadn’t realized Moose’s powerful delegation mechanisms we’re more than handy shortcuts. This provides an excellent use case for them.

      For those who don’t know Moose every attribute object can have a handles er … attribute … so the example here can be defined like:

      package Salesman;
      use Moose;
      
      has manager  => (
          ...
          handles => [qw( office )],
      );
      
      package Cusotomer;
      use Moose;
      
      has salesman => (
          isa => 'Salesm
      • Re: (Score:1)

        by avik (3911)

        Thanks for very thoughtful approach to teaching OO. Unfortunately, in my college days we learned OO in a worsed possible way (questionable faculty, clueless students, books never used).