Perl’s object system is very” flexible,” meaning that you get to build it from the ground up. You can build traditional hash-based objects, or more exotic forms, such as array-based or inside-out objects. However, in the two latter cases, you also have the onus to create the accessors, define access policies, and write a lot of repetitive code.
Luckily, Perl is introspective enough that you can get it to do most of the hard, boring work for you. Indeed, a number of simplifying” class frameworks” can now be found in the CPAN. The Moose framework appeared about a year ago, and I initially dismissed it as” yet another class framework”, much as I feel about yet another template system and yet another object-relational mapper (ORM).
However, I recently took a look at what Moose has become and was pleasantly surprised. As I started playing with it, I exclaimed frequently that Moose would have saved me quite a bit of time on some past projects, such as the text I wrote for the Intermediate Perl course and book, parts of which have been included as the perlbootman page in the Perl distribution.
Let’s recreate the” animal” classes from that text, using Moose, to see how this emerging framework simplifies things.
First, create a horse class in Horse.pm that has a name and a color:
package Horse; use Moose; has 'name' => (is => 'rw'); has 'color' => (is => 'rw'); 1;
Importing Moose defines has, which…
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