--- /dev/null
+# This module is part of DA, Don Armstrong's Modules, and is released
+# under the terms of the GPL version 2, or any later version. See the
+# file README and COPYING for more information. Copyright 2003 by Don
+# Armstrong <don@donarmstrong.com>.
+# $Id: Modular.pm,v 1.8 2003/12/09 02:00:10 don Exp $
+
+package Class::Modular;
+
+=head1 NAME
+
+Class::Modular -- Modular class generation superclass
+
+=head1 SYNOPSIS
+
+package Foo::Bar;
+
+@ISA = qw(Class::Modular);
+
+
+=head1 DESCRIPTION
+
+Class::Modular is a superclass for generating modular classes, where
+methods can be added into the class from the perspective of the
+object, rather than the perspective of the class.
+
+That is, you can create a class which has a set of generic common
+functions. Less generic functions can be included or overridden
+without modifying the base classes. This allows for code to be more
+modular, and reduces code duplication.
+
+=over
+
+=item new
+
+new is responsible for blessing and creating a new database superclass.
+
+=item load
+
+load is responsible for loading database plugins
+
+=back
+
+
+=head1 FUNCTIONS
+
+=cut
+
+use strict;
+use vars qw($VERSION $DEBUG);
+
+use Carp;
+
+use Data::Copy qw(deep_copy); # Used for deep copying objects
+
+BEGIN{
+ ($VERSION) = q$Revision: 1.8 $ =~ /\$Revision:\s+([^\s+])/;
+ $DEBUG = 0 unless defined $DEBUG;
+}
+
+our $AUTOLOAD;
+
+=head2 new
+
+ Title : new
+ Usage : $obj = Foo::Bar->new();
+ Function: Creates a new Foo::Bar object
+ Returns : A new Foo::Bar object
+ Args : none.
+
+ Aditional arguments can be passed to this creator, and they are
+ stored in $self->{_creation_args}. You can also override the new
+ method in your subclass. It's just provided here for completeness.
+
+=cut
+
+sub new {
+ my ($class,@args) = @_;
+
+ # We shouldn't be called $me->new, but just in case
+ $class = ref($class) || $class;
+
+ my $self = {};
+ bless $self, $class;
+
+ $self->_init(@args);
+
+ return $self;
+}
+
+
+=head2 _init
+
+=head3 Usage
+
+ $self->_init(@args);
+
+=head3 Function
+
+Stores the arguments used at new so modules that are loaded later can
+read them
+
+=cut
+
+sub _init {
+ my ($self,@creation_args) = @_;
+
+ $self->{creation_args} = [@_];
+}
+
+
+=head2 load
+
+ Title : load
+ Usage : $db->load('FOO::Subclass');
+ Function: loads a Class::Modular subclass
+ Returns : nothing
+ Args : SCALAR subclass SCALAR options
+
+ Loads the named subclass into this object if the named subclass has
+ not been loaded.
+
+ The options scalar is passed to $subclass::_methods when determining
+ which methods should be added using _addmethods.
+
+ The subclasses _init method is called right after methods are loaded.
+
+ If debugging is enabled, will warn about loading already loaded
+ subclasses.
+
+=cut
+
+
+sub load($$;$) {
+ my ($self,$subclass,$options) = @_;
+
+ $options ||= {};
+
+ # check to see if the subclass has already been loaded.
+
+ if (not defined $self->{_subclasses}->{$subclass}){
+ eval {
+ no strict 'refs';
+ eval "require $subclass" or die $@;
+ $self->_addmethods($subclass,&{"${subclass}::_methods"}($self,$options));
+ &{"${subclass}::_init"}($self);
+ };
+ die $@ if $@;
+ $self->{_subclasses}->{$subclass} = {};
+ }
+ else {
+ carp "Not reloading subclass $subclass" if $DEBUG;
+ }
+}
+
+=head2 _addmethods
+
+ Title : _addmethods
+ Usage : $self->_addmethods()
+ Function: Adds the passed methods into the function table
+ Returns :
+ Args : ARRAY of methods
+
+ Given an array of methods, adds the methods into the _methodhash
+ calling table.
+
+ Methods that have previously been overridden by override are _NOT_
+ overridden again. This may need to be adjusted in load.
+
+=cut
+
+sub _addmethods($@) {
+ my ($self,$subclass,@methods) = @_;
+
+ # stick the method into the table
+ # DLA: Make with the munchies!
+
+ foreach my $method (@methods) {
+ if (not $method =~ /^$subclass/) {
+ $method = $subclass.'::'.$method;
+ }
+ my ($method_name) = $method =~ /\:*([^\:]+)\s*$/;
+ if (exists $self->{_methodhash}->{$method_name}) {
+ if ($self->{_methodhash}->{$method_name}->{overridden}) {
+ carp "Not overriding already overriden method $method_name\n" if $DEBUG;
+ next;
+ }
+ carp "Overriding $method_name $self->{_methodhash}->{$method_name}->{reference} with $method\n";
+ }
+ $self->{_methodhash}->{$method_name}->{reference} = $method;
+ $self->{_methodhash}->{$method_name}->{subclass} = $subclass;
+ }
+
+}
+
+=head2 override
+
+ Title : override
+ Usage : $obj->override('methodname', $code_ref)
+ Function: Overrides the method methodname and calls $code_ref instead.
+ Returns : TRUE on success, FALSE on failure.
+ Args : SCALAR method name
+ CODEREF function reference
+
+ Allows you to override utility functions that are called internally
+ to provide a different default function.
+
+ It's superficially similar to _addmethods, which is called by load,
+ but it deals with code references, and requires the method name to be
+ known.
+
+ Methods overridden here are _NOT_ overrideable in _addmethods. This
+ may need to be changed.
+
+=cut
+
+sub override {
+ my ($self, $method_name, $function_reference) = @_;
+
+ $self->{_methodhash}->{$method_name}->{reference} = $function_reference;
+ $self->{_methodhash}->{$method_name}->{overridden} = 1;
+}
+
+=head2 clone
+
+ Title : clone
+ Usage : my $clone = $obj->clone
+ Function: Produces a clone of the Class::Modular object
+ Returns :
+ Args :
+
+ Produces a clone of the object with duplicates of all data and/or new
+ connections as appropriate.
+
+ Calls _clone on all loaded subclasses.
+
+ Warns if debugging is on for classes which don't have a _clone
+ method. Dies on other errors.
+
+=cut
+
+sub clone {
+ my ($self) = @_;
+
+ my $clone = {};
+ bless $clone, ref($self);
+
+ # copy data structures at this level
+ $clone->{_methodhash} = deep_copy($self->{_methodhash});
+ $clone->{_subclasses} = deep_copy($self->{_subclasses});
+
+ foreach my $subclass (keys %{$self->{_subclasses}}) {
+ # use eval to try and call the subclasses _clone method.
+ # Ignore no such function errors, but trap other types of
+ # errors.
+
+ # XXX Switch to can instead.
+ eval {
+ no strict 'refs';
+ &$subclass::_clone($self,$clone);
+ };
+ if ($@) {
+ # Die unless we've hit an undefined subroutine.
+ die $@ unless $@ =~ /Undefined\s*subroutine\s*\&.*\:\:\_clone/;
+ warn "$subclass doesn't have a _clone method\n$@" if $DEBUG;
+ }
+
+
+ }
+}
+
+=head2 can
+
+=head3 Usage
+
+ $obj->can('METHOD');
+ Class::Modular->can('METHOD');
+
+=head3 Function
+
+Replaces UNIVERSAL's can method so that handled methods are reported
+correctly. Calls UNIVERSAL::can in the places where we don't know
+anything it doesn't.
+
+=head3 Returns
+
+A coderef to the method if the method is supported, undef otherwise.
+
+=head3 Args
+
+Scalar Method Name
+
+=cut
+
+sub can{
+ my ($self,$method,$vars) = @_;
+
+ if (ref $self and exists $self->{_methodhash}->{$method}) {
+ # If the method is defined, return a reference to the
+ # method.
+ return $self->{_methodhash}->{$method}->{reference};
+ }
+ else {
+ # Otherwise, let UNIVERSAL::can deal with the method
+ # appropriately.
+ return UNIVERSAL::can($self,$method);
+ }
+}
+
+=head2 handledby
+
+=head3 Usage
+
+ $obj->handledby('methodname');
+ $obj->handledby('Class::Method::methodname');
+
+=head3 Function
+
+Returns the subclass that handles this method.
+
+=head3 Returns
+
+SCALAR subclass name
+
+=head3 Args
+
+SCALAR method name
+
+=cut
+
+sub handledby{
+ my ($self,$method_name) = @_;
+
+ $method_name =~ s/.*\://;
+
+ if (exists $self->{_methodhash}->{$method_name}) {
+ return $self->{_methodhash}->{$method_name}->{subclass};
+ }
+ return undef;
+}
+
+
+=head2 DESTROY
+
+=head3 Usage
+
+Called by perl.
+
+=head3 Function
+
+Calls all subclass _destroy methods.
+
+Subclasses need only implement a _destroy method if they have
+references that need to be uncircularized, or things that should be
+disconnected or closed.
+
+=cut
+
+sub DESTROY{
+ my $self = shift;
+ foreach my $subclass (keys %{$self->{_subclasses}}) {
+ # use eval to try and call the subclasses _destroy method.
+ # Ignore no such function errors, but trap other types of
+ # errors.
+ eval {
+ no strict 'refs';
+ &$subclass::_destroy($self);
+ };
+ if ($@) {
+ # Die unless we've hit an undefined subroutine.
+ die $@ unless $@ =~ /Undefined\s*subroutine\s*\&.*\:\:\_clone/;
+ warn "$subclass doesn't have a _clone method\n$@" if $DEBUG;
+ }
+ }
+}
+
+
+=head2 AUTOLOAD
+
+ Title : AUTOLOAD
+ Usage : Called by perl
+ Function: Calls child methods which have been installed into this handle
+ Returns : N/A
+ Args : N/A
+
+The AUTOLOAD function is responsible for calling child methods which
+have been installed into the current Class::Modular handle.
+
+Subclasses that have a new function as well as an AUTOLOAD function
+must call Class::Modular::AUTOLOAD and set $Class::Modular::AUTOLOAD
+
+ $Class::Modular::AUTOLOAD = $AUTOLOAD;
+ goto &Class::Modular::AUTOLOAD;
+
+=cut
+
+sub AUTOLOAD{
+ my $method = $AUTOLOAD;
+
+ $method =~ s/.*\://;
+
+ my ($self) = @_;
+
+ if (not ref($self)) {
+ carp "Not a reference in AUTOLOAD.";
+ return;
+ }
+
+ if (exists $self->{_methodhash}->{$method} and
+ defined $self->{_methodhash}->{$method}->{reference}) {
+ eval {
+ no strict 'refs';
+ goto &{$self->{_methodhash}{$method}{reference}};
+ }
+ }
+ else {
+ croak "Undefined function $AUTOLOAD";
+ }
+}
+
+
+1;
+
+
+__END__
+
+
+
+
+
+
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