Class::Spiffy 0.15

Class::Spiffy is a Spiffy Framework with No Source Filtering.

SYNOPSIS

package Keen;
use strict;
use warnings;
use Class::Spiffy -base;
field mirth;
const mood => :-);

sub happy {
my $self = shift;
if ($self->mood eq :-() {
$self->mirth(-1);
print "Cheer up!";
}
super;
}

1;

"Class::Spiffy" is a framework and methodology for doing object oriented (OO) programming in Perl. Class::Spiffy combines the best parts of Exporter.pm, base.pm, mixin.pm and SUPER.pm into one magic foundation class. It attempts to fix all the nits and warts of traditional Perl OO, in a clean, straightforward and (perhaps someday) standard way.

Class::Spiffy borrows ideas from other OO languages like Python, Ruby, Java and Perl 6. It also adds a few tricks of its own.

If you take a look on CPAN, there are a ton of OO related modules. When starting a new project, you need to pick the set of modules that makes most sense, and then you need to use those modules in each of your classes. Class::Spiffy, on the other hand, has everything youll probably need in one module, and you only need to use it once in one of your classes. If you make Class::Spiffy the base class of the basest class in your project, Class::Spiffy will automatically pass all of its magic to all of your subclasses. You may eventually forget that youre even using it!

The most striking difference between Class::Spiffy and other Perl object oriented base classes, is that it has the ability to export things. If you create a subclass of Class::Spiffy, all the things that Class::Spiffy exports will automatically be exported by your subclass, in addition to any more things that you want to export. And if someone creates a subclass of your subclass, all of those things will be exported automatically, and so on. Think of it as "Inherited Exportation", and it uses the familiar Exporter.pm specification syntax.
To use Class::Spiffy or any subclass of Class::Spiffy as a base class of your class, you specify the -base argument to the use command.

use MySpiffyBaseModule -base;

You can also use the traditional use base MySpiffyBaseModule; syntax and everything will work exactly the same. The only caveat is that Class::Spiffy must already be loaded. Thats because Class::Spiffy rewires base.pm on the fly to do all the Spiffy magics.

Class::Spiffy has support for Ruby-like mixins with Perl6-like roles. Just like base you can use either of the following invocations:

use mixin MySpiffyBaseModule;
use MySpiffyBaseModule -mixin;

The second version will only work if the class being mixed in is a subclass of Class::Spiffy. The first version will work in all cases, as long as Class::Spiffy has already been loaded.

To limit the methods that get mixed in, use roles. (Hint: they work just like an Exporter list):

use MySpiffyBaseModule -mixin => qw(:basics x y !foo);

A useful feature of Class::Spiffy is that it exports two functions: field and const that can be used to declare the attributes of your class, and automatically generate accessor methods for them. The only difference between the two functions is that const attributes can not be modified; thus the accessor is much faster.

One interesting aspect of OO programming is when a method calls the same method from a parent class. This is generally known as calling a super method. Perls facility for doing this is butt ugly:

sub cleanup {
my $self = shift;
$self->scrub;
$self->SUPER::cleanup(@_);
}

Class::Spiffy makes it, er, super easy to call super methods. You just use the super function. You dont need to pass it any arguments because it automatically passes them on for you. Heres the same function with Class::Spiffy:

sub cleanup {
my $self = shift;
$self->scrub;
super;
}

Class::Spiffy has a special method for parsing arguments called parse_arguments, that it also uses for parsing its own arguments. You declare which arguments are boolean (singletons) and which ones are paired, with two special methods called boolean_arguments and paired_arguments. Parse arguments pulls out the booleans and pairs and returns them in an anonymous hash, followed by a list of the unmatched arguments.

Finally, Class::Spiffy can export a few debugging functions WWW, XXX, YYY and ZZZ. Each of them produces a YAML dump of its arguments. WWW warns the output, XXX dies with the output, YYY prints the output, and ZZZ confesses the output. If YAML doesnt suit your needs, you can switch all the dumps to Data::Dumper format with the - dumper option.