Class::Adapter::Clear (3pm)

Hello World with \s-1CGI\s0.pm the normal way

  # Load and create the CGI
  use CGI;
  $q = new CGI;

  # Create the page
  print $q->header,                    # HTTP Header
        $q->start_html('hello world'), # Start the page
        $q->h1('hello world'),         # Hello World!
        $q->end_html;                  # End the page

Hello World with \s-1CGI\s0.pm the Adapter'ed way

# Load and create the CGI use CGI; $q = new CGI;

# Convert to an Adapter use Class::Adapter::Clear; $q = new Class::Adapter::Clear( $q );

# Create the page print $q->header, # HTTP Header $q->start_html('hello world'), # Start the page $q->h1('hello world'), # Hello World! $q->end_html; # End the page

Creating a \s-1CGI\s0 Adapter class using Class::Adapter::Clear

package My::CGI;

use base 'Class::Adapter::Clear';

# Optional - Create the thing we are decorating auto-magically sub new { my $class = shift;

# Create the object we are decorating my $query = CGI->new(@_);

# Wrap it in the Adapter $class->SUPER::new($query); }

# Decorate the h1 method to change what is created sub h1 { my $self = shift; my $str = shift;

# Do something before the real method call if ( defined $str and $str eq 'hello world' ) { $str = 'Hello World!'; }

$self->_OBJECT_->($str, @_); }

\*(C`Class::Adapter::Clear\*(C' provides the base class for creating one common type of Class::Adapter classes. For more power, move up to Class::Adapter::Builder.

On it's own \*(C`Class::Adapter::Clear\*(C' passes all methods through to the same method in the parent object with the same parameters, responds to \*(C`->isa\*(C' like the parent object, and responds to \*(C`->can\*(C' like the parent object.

It looks like a \*(C`Duck\*(C', and it quacks like a \*(C`Duck\*(C'.

On this base, you simple implement whatever method you want to do something special to.

# Different method, same parameters sub method1 { my $self = shift; $self->_OBJECT_->method2(@_); # Call a different method }

# Same method, different parameters sub method1 { my $self = shift; $self->_OBJECT_->method1( lc($_[0]) ); # Lowercase the param }

# Same method, same parameters, tweak the result sub method1 { my $self = shift; my $rv = $self->_OBJECT_->method1(@_); $rv =~ s/\n/<br>\n/g; # Add line-break HTML tags at each newline return $rv; }

As you can see, the advantage of this full-scale Adapter approach, compared to inheritance, or function wrapping (see Class::Hook), is that you have complete and utter freedom to do anything you might need to do, without stressing the Perl inheritance model or doing anything unusual or tricky with \*(C`CODE\*(C' references.

You may never need this much power. But when you need it, you really need it.

As an aside, Class::Adapter::Clear is implemented with the following Class::Adapter::Builder formula.

use Class::Adapter::Builder ISA => '_OBJECT_', AUTOLOAD => 1;

As does the base Class::Adapter class, the default \*(C`new\*(C' constructor takes a single object as argument and creates a new object which holds the passed object.

Returns a new \*(C`Class::Adapter::Clear\*(C' object, or \*(C`undef\*(C' if you do not pass in an object.

Bugs should be reported via the \s-1CPAN\s0 bug tracker at

<http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Class-Adapter>

For other issues, contact the author.

Adam Kennedy <[email protected]>

Class::Adapter, Class::Adapter::Builder

Copyright 2005 - 2010 Adam Kennedy.

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

The full text of the license can be found in the \s-1LICENSE\s0 file included with this module.