in reply to Re: Where/When is OO useful?
in thread Where/When is OO useful?
Another object idiom: this one, people tell me is aweful.
I like it a lot because it overcomes something I hate
about Perl: how object instance data requires lots
of funny syntax. This syntax makes it tedious to refactor
code from a subroutine into a method.
Like Abagail's, it uses lexicals to
good effect. It requires some glue, but class fields are
then normal lexical variables. The object is a blessed
hash - but instead of data, the hash holds the methods.
The AUTOLOAD glue just dispatches to the correct hash
element. The glue sets $self, so it is not necessary to
read it off of the argument list manually, should it
be needed (for a method call, for example).
Primary drawbacks are a small speed penalty - but for very small data classes like this, I tend to use rather ordinary blessed arrays, anyway, or psuedohashes, or "use fields" pragmatic module (all about the same thing right now - psuedohashes will be going away I'm told). Code inheritance works - however, fields declared lexically like this aren't inherited. All data is essentially private. I find this just as well - it forces a subclass to use its parents accessors. Finally, you have to be somewhat accustomed to Functional Programming to be used to staring at indenting like that. This is just a brief restatement of the second half of Anonymous Subroutine Objects at PerlDesignPatterns.com. I treat the AUTOLOAD footer as a Wrapper Module, and just use it into my namespace.sub new { my $ERA; my $Strikeouts; bless { get_ERA => sub { $ERA }, set_ERA => sub { $ERA = shift }, get_Strikeouts => sub { $Strikeouts }, set_Strikeouts => sub { $Strikeouts = shift }, }, shift(); } sub AUTOLOAD { (my $method) = $AUTOLOAD =~ m/::(.*)$/; return if $method eq 'DESTROY'; our $this = shift; if(! exists $this->{$method}) { my $super = "SUPER::$method"; return $this->$super(@_); } $this->{$method}->(@_); } 1;
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