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Ovid (2709)

Ovid
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Stuff with the Perl Foundation. A couple of patches in the Perl core. A few CPAN modules. That about sums it up.

Journal of Ovid (2709)

Sunday December 04, 2005
03:17 AM

Refactoring into oblivion

[ #27851 ]

So I stumbled across the following:

sub schema_for_class {
  my ( $self, $class ) = @_;
  return grep { $_ }
    $self->table_for_class($class),
    $self->indexes_for_class($class),
    $self->constraints_for_class($class),
    $self->view_for_class($class),
    $self->insert_for_class($class),
    $self->update_for_class($class),
    $self->delete_for_class($class);
}

That's a lot of repetition and therefore a lot of noise. So I reworked it a bit.

sub schema_for_class {
  my ( $self, $class ) = @_;
  return
    grep { $_ }
      map {
        my $method = "${_}_for_class";
        $self->$method($class)
      } qw(
        table
        indexes
        constraints
        view
        insert
        update
        delete
      );
}

Now I feel like a maintenance programmer can glance at it and get an idea of what's going on. But I do worry that sometimes I'm refactoring so aggressively that maybe it's getting too abstract. I do try and find a balance. I'm just not sure that I balance quite where others do.


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  • I did a similar refactoring just tonight with far fewer similar method names.

    • With all due respect, I know you're going to get it. I've seen your work (hell, I've worked with you) and I know that you won't blink when you see that. I just worry about the poor maintenance programmer. I'm not too terribly worried as I think that the maintenance programmer who works on this code had better be pretty damned nimble with the Perl chainsaw in the first place, but then, I'm so used to seeing this that I've no idea if it's obscure or not.

  • You're right that different people will draw the line in different places. I think that the original is actually better code, because it's immediately obvious what it does. The refactored version requires a bit of “decoding”.

    The important thing is that you’re thinking about it rather than just refactoring it because you can. (And I guess that this example must be close to your own borderline, or you wouldn't be asking about it.)

  • fifthed: IMO you've taken something very straightforward and made it something to stumble over for no real benefit. And Chris's note about making your method calls ungreppable (or ctaggable) should make this an easy undo.

  • I share your instinct and to refactor this, but your refactored version would strike me as odd immediately upon finding it: why grep { $_ } map { $foo } when that’s exactly the same as grep { $foo }?

    And I think the interpolation is just too clever. It also makes it unnecessarily hard to add or remove method calls that may not follow this naming scheme, should that ever be necessary. So I’d simply say

    sub schema_for_class {
        my $self = shift;
            my ( $class

    • (No, I didn’t intentionally forget to convert the spaces to a tab in my ( $class ) = @_;.)

    • Isn't the return value from your version simply going to be:
      qw(
                      table_for_class
                      indexes_for_class
                      constraints_for_class
                      view_for_class
                      insert_for_class
                      update_for_class
       

      • Ack! Of course. Sigh.

        I guess one could use

        map {
            my $method = $_;
            $self->$method( $class ) || ();
        } @method;

        but I’m not sure how well advised that is…

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