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__END__

=head1 NAME

Badger::Prototype - base class for creating prototype classes

=head1 SYNOPSIS

    package Badger::Example;
    use base 'Badger::Prototype';
    
    sub greeting {
        my $self = shift;
        
        # get prototype object if called as a class method
        $self = $self->prototype() unless ref $self;
        
        # continue as normal, now $self is an object
        if (@_) {
            # set greeting if called with args
            return ($self->{ greeting } = shift);
        }
        else {
            # otherwise get greeting
            return $self->{ greeting };
        }
    }

=head1 DESCRIPTION

This module is a subclass of L<Badger::Base> that additionally provides
the L<prototype()> method.  It is used as a base class for modules that
have methods that can be called as either class or object methods.

    # object method
    my $object = Badger::Example->new();
    $object->greeting('Hello World');

    # class method
    Badger::Example->greeting('Hello World');

The L<prototype()> method returns a singleton object instance which can be 
used as a default object by methods that have been called as class methods. 

Here's an example of a C<greeting()> method that can be called with an argument 
to set a greeting message:

    $object->greeting('Hello World');

Or without any arguments to get the current message:

    print $object->greeting;            # Hello World

As well as being called as an object method, we want to be able to call it
as a class method:

    Badger::Example->greeting('Hello World');
    print Badger::Example->greeting();  # Hello World

Here's what the C<greeting()> method looks like.

    package Badger::Example;
    use base 'Badger::Prototype';
    
    sub greeting {
        my $self = shift;
        
        # get prototype object if called as a class method
        $self = $self->prototype() unless ref $self;
        
        # continue as normal, now $self is an object
        if (@_) {
            # set greeting if called with args
            return ($self->{ greeting } = shift);
        }
        else {
            # otherwise get greeting 
            return $self->{ greeting };
        }
    }

We use C<ref $self> to determine if C<greeting()> has been called as an object
method (C<$self> contains an object reference) or as a class method (C<$self>
contains the class name, in this case C<Badger::Example>). In the latter
case, we call L<prototype()> as a class method (remember, C<$self> contains
the C<Badger::Example> class name at this point) to return a prototype 
object instance which we then store back into C<$self>.

        # get prototype object if called as a class method
        $self = $self->prototype() unless ref $self;

For the rest of the method we can continue as if called as an object 
method because C<$self> now contains a C<Badger::Example> object
either way.

Note that the prototype object reference is stored in the C<$PROTOTYPE>
variable in the package of the calling object's class.  So if you call
prototype on a C<Badger::Example::One> object that is subclassed from 
C<Badger::Prototype> then the prototype object will be stored in the 
C<$Badger::Example::One::PROTOTYPE> package variable.

=head1 METHODS

=head2 prototype(@args)

Constructor method to create a prototype object and cache it in the
C<$PROTOTYPE> package variable for subsequent use.  This is usually 
called from inside methods that can operate as class or object methods, 
as shown in the earlier example.

    sub example {
        my $self = shift;
        
        # upgrade $self to an object when called as a class method
        $self = $self->prototype() unless ref $self;
        
        # ...code follows...
    }

If you prefer a more succinct idiom and aren't too worried about calling the