NAME
Class::MixinFactory::alternatives - approaches to the same functionality
DESCRIPTION
A recent contribution to CPAN is Class::MixinFactory by Simon Cavaletto.
Here we show two more ways to do the same thing in addition to the ones
that Simon lists in the SEE ALSO section.
One method relies on Leon Brocard's Language::Functional. The other
relies on Toby Ovod-Everett's Class::Prototyped.
ALTERNATIVE IMPLMENTATIONS
I include here a file, which when run, produces output similar to the
output from factory_class.t in the Class::MixinFactory distribution.
It shows two new ways of doing this, the Language::Functional approach
and the Class::Prototyped approach.
#
# lf.pl
#
use strict;
use Language::Functional ':all';
sub _uc { uc shift } ;
sub bold { sprintf "<b>%s</b>", shift } ;
sub italics { sprintf "<i>%s</i>", shift } ;
my @telescope = (\&_uc, \&bold, \&italics) ;
my $o = foldl { my $seed = shift; my $func = shift; $func->($seed) }
"hello, world!", [EMAIL PROTECTED];
warn $o;
# ----------------------------------------------------------
use Class::Prototyped ':EZACCESS';
sub add2 { $_[1] + 2 };
my $po;
$po = Class::Prototyped->new
(
uc_m => sub { uc $_[1] },
italics_m => sub { italics $_[1] },
bold_m => sub { bold $_[1] }
);
my @agenda = qw(uc_m italics_m);
my @agenda2 = qw(bold_m italics_m uc_m);
my $ret = foldl { my $seed = shift; my $meth = shift; $po->$meth($seed) }
"hello, world!", [EMAIL PROTECTED];
warn $ret;
$ret = foldl { my $seed = shift; my $meth = shift; $po->$meth($seed) }
"hello, world!", [EMAIL PROTECTED];
warn $ret;
EVALUATION
We can compare these two implementations in a number of ways -
readability, dynamic utility, object power, and sub power.
Readability
Of the two implementations, the functional implementation is the easiest
to read and follow.
Dynamic utility
The prototype implementation appears to be easier to manipulate
dynamically. What I mean by easier to manipulate dynamically is that all
one need do is specify a list of strings in order to build up a sequence
of operations. Strings can come from many places, such as form data,
databases, STDIN, etc. With the functional version, you would need to
build yourself a dispatch table in order to get similar functionality.
The table building is an intrinsic aspect of using Class::Prototyped. It
must be done manually for the functional version.
Object power
Prototyped objects are powerful and flexible. They give one the
advantage of objects without all the class-building. The functional
version will not have the advantages of prototyped objects without
creating objects and then references to the subroutines of those objects
(I don't even know if that is possible).
Sub power
An advantage of the functional implementation is that you can use normal
monadic functions just by passing a reference to them. With the
prototyped implementation, you have to create an object wrapper for
them.
CONCLUSION
Perl offers a wealth of ways to solve problems. Simon's recent
Class::MixinFactory solved a number of problems with the Mixin approach
to runtime generation of "agendas for mixing behavior." He also makes
mention of a number of other approaches and perhaps should mention
Class::Delegation in addition.
In this article, I have shown two more ways to mix behavior. The actual
one to choose for software design remains open based on other aspects of
the intended application.
SEE ALSO
* Language::Functional
* Class::Prototyped
* CGI::Prototype
That's right, if you like the prototyped way of doing this, there is
a web application framework developed by Randal Schwartz which is
based on Class::Prototyped. It is well thought out, well-designed
and covers the functionality offered by earlier MVC frameworks with
powerful, featureful controllers such as CGI::Application and Zanas.
* The Perl Software::Design Mailing list
<http://www.metaperl.com/sw-design/>
AUTHOR
U-MOKSHA\metaperl, <[EMAIL PROTECTED]>
COPYRIGHT AND LICENSE
Copyright (C) 2004 by U-MOKSHA\metaperl
This library is free software; you can redistribute it and/or modify it
under the same terms as Perl itself, either Perl version 5.8.2 or, at
your option, any later version of Perl 5 you may have available.
To download the CPAN-style distro with working source code, visit:
http://www.metaperl.com/article-pod/Class-MixinFactory-alternatives-0.01.tar.gz
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