Perl6::Attributes - Perl 6-like member variable syntax
package Foo; use Perl6::Attributes; sub new { my ($class) = @_; bless { a => 1, b => [ 2, 3, 4 ], c => { hello => "World" }, } => ref $class || $class; } sub example { my ($self) = @_; $.a; # 1 $.b[2]; # 4 @.b; # 2 3 4 $#.b; # 3 $.c{hello}; # World keys %.c; # hello print "I get the idea"; }
I found myself annoyed when I wrote the following code in one of my recent projects:
sub populate { my ($self, $n) = @_; for (1..$n) { push @{$self->{organisms}}, Organism->new(rand($self->{width}), rand($self->{height})); } }
Three $selfs in one line! And it's really not encoding any information, it's just clutter that results from Perl's lack of explicit object-oriented support. However, Using the magic of source filters, we can now write it:
$self
sub populate { my ($self, $n) = @_; for (1..$n) { push @.organisms, Organism->new(rand($.width), rand($.height)); } }
Perl6::Attributes takes the Perl 6 secondary sigil . and translates it into a hash access on $self. No, it doesn't support other names for your invocant (but it could very easily; I'm just lazy), and no, it doesn't support objects written by crazy people based on array, scalar, or (!) glob references.
.
You still inflect the primary sigil, unlike in Perl 6. See Perl6::Variables for a way to use Perl 6's uninflected sigils... but don't expect it to work with this module.
There's also a nice little "feature" that you get for trading the ability to name your variables the same with different sigils (by the way, you can't do that). Say $self->{foo} is an array ref:
@.foo; # the array itself $.foo; # the reference
Which means that even if you're using an array referentially, you can usually avoid writing those pesky @{}s everywhere.
@{}
Perl6::Attributes now also translates ./method and ./method(args) to $self-method> and $self-method(args)>.
./method
./method(args)
$self-
Perl6::Variables, Lexical::Attributes
Luke Palmer <luke@luqui.org>
Copyright (C) 2005 by Luke Palmer This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself, either Perl version 5.8.3 or, at your option, any later version of Perl 5 you may have available.
To install Perl6::Attributes, copy and paste the appropriate command in to your terminal.
cpanm
cpanm Perl6::Attributes
CPAN shell
perl -MCPAN -e shell install Perl6::Attributes
For more information on module installation, please visit the detailed CPAN module installation guide.