Update: How bizarre! I haven't been on Perlmonks all day, but I come here to make this weird post only to discover (after I post) a freakishly similar idea discussed today.

An interesting talk with a coworker about Smalltalk has inspired me to think about a new, rather curious module.

Often, when working on a project, I have many related packages. It can get awfully annoying to find this at the top of all of my code:

use Foo::Dates;
use Foo::Customer;
use Foo::Order;
use Foo::Company;
use Foo::Company::SalesReps;
use Foo::Extremely::Long::Package::Name;

[download]

In Smalltalk, you just use (as in "make use of", not to be confused with Perl's keyword "use") the classes. In Java, there is at least a useful import keyword:

import Foo.*;

I started to wonder why I can't do that in Perl. After talking to him about implementations, I took a snippet he wrote and came up with something like the following code:

sub HTML::TokeParser::Simple
{
    my $module = (caller(0))[3];
    undef *{$module};
    eval "require $module";
    if ($@) {
        require Carp;
        Carp::croak "No such module: $module";
    }
    return $module;
}

package main;
my $parser = HTML::TokeParser::Simple->new(\*DATA);

__DATA__
<html>
  <head>
  ... more html

[download]

If you don't understand that code, what it does is create a function in the "HTML::TokeParser" namespace that undefs itself (so it won't be called more than once), uses the class in question and then returns the fully qualified name as a string.

So what if I were to create a module that did something like this:

use Class::WhenNeeded 'Foo';

my $customer = Foo::Customer->new($customer_id);
my $order    = Foo::Order->new;

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In other words, we can skip the long lists of "use" and require declarations. I specifically mention "Class" in the package name as I expect that function oriented modules would be more difficult to manage due to exporting issues.

Another interface -- but more dangerous since it could have namespace collisions if you use subs with upper-case first letters:

use Class::WhenNeeded Foo => 'no_top_level';

my $customer = Customer->new($customer_id);
my $order    = Order->new;

[download]

Can anyone think of strong reasons why this would or would not be a good idea? I can see some problems with this, but it's an interesting idea.

Problems:

Cheers,
Ovid

New address of my CGI Course.

In reply to DWIM: autoloading classes by Ovid

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