Provided by: libclass-ooorno-perl_0.011-3_all 
NAME
Class::OOorNO - Give your module classic AND OO interfaces
STATUS!
This is a developer's release, and is not intended for use in the public sector. This
code is made available for developers who wish to aid in the furthering of the code.
This is not a registered module in the CPAN module list. It is not part of the CPAN yet.
SYNOPSIS
Functional programming interface
package Your::Class;
use Class::OOorNO qw( coerce_array );
Object-Oriented programming interface
package Your::Class;
use Class::OOorNO;
my($obj) = Class::OOorNO->new();
Class Inheritance
package Your::Class;
use vars qw( @ISA );
use Class::OOorNO;
@ISA = qw( Class::OOorNO );
PURPOSE
Allows you set up your module so it can easily provide a standard interface as well as an
object-oriented interface to its users.
DESCRIPTION
Class::OOorNO helps your module handle the input for its subroutines whether called in
object-oriented style (as object methods or class methods with the arrow syntax "->"), or
in functional programming style (as subroutines imported to the caller's namespace via
Exporter).
The bulk of this module comprises a lightweight, pure-Perl emulation of the Devel::Caller
library's "called_as_method()" routine which is written in C.
Devel::Caller dives deep into the internals of of the Perl interpreter (see perlguts) to
trace stack frames and can get the input for any call in the stack. It's really handy for
Devel::opment and debugging.
This module is much more lightweight and focuses more on your module's Class:: methods
themselves.
EXPORT
None by default.
EXPORT_OK
All available methods. (see METHODS below)
EXPORT_TAGS
":all" (exports all of @EXPORT_OK)
METHODS
"myself()"
Syntax: "myself(@_)"
If your subroutine has been called as an object method, a reference to the object will
be returned. If your subroutine has been called as a class method, the name of class
itself will be returned as a string. Otherwise, a value of undef is returned.
"OOorNO()"
Syntax: "OOorNO(@_)"
If your subroutine has been called as an object method or as a class method, a value
of 1 will be returned, otherwise a false value (an empty string, eg- '') will be
returned.
"myargs()"
Syntax: "myargs(@_)"
This method retrieves the input sent to your class methods and returns it untouched,
with the exception that if a blessed object reference from the same namespace as the
caller is found in $_[0], it will be not be included with the rest of the arguments
when they are returned. Make note that the special variable "@_" for your routine is
not altered in any way by calling this method. You can still use and manipulate it as
you normally would.
Purpose of "OOorNO::myargs"
This simply allows the methods in your class to get their argment list quickly without
having to check if they were called procedurally or with object-oriented notation.
Caveat:
If you are expecting a blessed object reference from your package to be in $_[0]
regardless of the way your method was called -don't use this method to get your
arguments; that reference you're expecting will obviously be excluded from the
list you get back from "myargs" if you do.
package Your::Class;
use Class::OOorNO qw( myargs );
sub bar {
my(@args) = myargs(@_);
...
-OR-
package Your::Class;
use Class::OOorNO;
our($onobj) = Class::OOorNO->new();
sub foo {
my(@args) = $onobj->myargs(@_);
...
"coerce_array()"
Syntax: "coerce_array(@array/(list))"
This method retrieves input sent to your class methods when called with name-value
pairs and returns an anonymous hash reference whose keys and values correspond to the
input argument names and their respective values. If nothing is passed to it, an
empty hash reference will be returned, eg- "{ }"
package Your::Class;
use Class::OOorNO qw( coerce_array );
sub bar {
my($args) = coerce_array(@_);
...
-OR-
package Your::Class;
use Class::OOorNO;
our($onobj) = Class::OOorNO->new();
sub foo {
my($self) = shift(@_);
my($args) = $onobj->coerce_array(@_);
...
-OR-
package Your::Class;
use Class::OOorNO;
use vars qw( @ISA );
@ISA = qw( Class::OOorNO );
sub foo {
my($self) = shift(@_);
my($args) = $self->coerce_array(@_);
...
Purpose of "OOorNO::coerce_array"
It's common practice for Perl modules to accept name-value pairs for their methods,
and because @_ is an array it is easy to encounter warnings and errors when this isn't
handled correctly. An example of what this kind of call would look like is shown
below in the imaginary subroutine "Your::Class::method()"
Your::Class->method
(
-name => 'Joe',
-rank => 'Private, First-Class',
-SN => '87D91-35-713FOO',
);
Avoids Common Pitfalls
Quite often a class method will use code such as this to handle name-value paired
input:
sub foo {
my($class) = shift;
my(%args) = @_; ...
-and/or-
sub bar {
my($args) = { @_ }; ...
What's Wrong With That?
While this practice is not evil, it can be error-prone in situations where:
• Your class method is called in procedural style and expects that the first
element in @_ is a blessed object reference.
• Your class method is errantly called with an unbalanced set of name-value
pairs, or one or more named arguments get passed with undefined values.
• You want to give your module the ability to export any or all of its methods
by using the Exporter module, but still want to maintain an object-oriented
interface to your module as well. An example of a well known module which
does this is CGI.pm. It is written to provide both a standard procedural
interface as well as an object-oriented one. You can call its methods either
way:
# object-oriented style
use CGI;
my($cgi_object) = CGI->new();
my($visitor) = $cgi_object->param('visitor name');
-OR-
# procedural style
use CGI qw( param );
my($visitor) = param('visitor name');
Don't say I didn't warn you ;o)
When these situations occur, class methods sorting out name-value paired input
using the common problematic technique (demonstrated above in "Pitfalls)"
encounter problems such as undesired program behavior, general errors, and
warnings -both fatal and non-fatal. Problems include:
• Argument sets that get reversed; the argument names become the hash values and
the argument values become the hash keys which is exactly the opposite of the
desired behavior.
• The entire arument hash/hashref gets turned into a mess of mixed up keys and
values that don't reflect the actual input at all. Instead, you get hash keys
containing both argument names and argument values.
• The argument hash/hashref is created with an uneven number of elements and/or
uninitialized values.
Warnings (see perldiag) resulting from the above mentioned situations could
include any the following (Some of these don't apply unless you run your program
under the warnings pragma) like you should.
"Can't coerce array into hash"
This is a fatal warning, eg- if you see it your program failed and execution
aborted.)
"Odd number of elements in hash assignment"
non-fatal.
"Not a %s reference"
-where %s is probably "HASH", though it could be complaining about a non-
reference to any data type that your routine may be attempting to treat as a
reference. This is often the result of a class method being called in
procedural style rather than in the object-oriented style using the arrow
"-\"> syntax. The class method expects the first argument to be an object
reference, when it is clearly not. (This warning is fatal as well.)
"Can't call method %s on unblessed reference"
This is another a fatal warning, and will occur under the same circumstances
that surround the warning described immediately above. The class method
expects the first argument to be an object reference when it's not.
"shave_opts()"
Syntax: "shave_opts(\@_)"
-- Documentation for this method is not yet complete! --
EXAMPLES
Note: This is not a complete set of examples. It's still evolving.
using "OOorNO()"
Your module...
package Your::Module;
use strict;
use Exporter;
use vars qw( @EXPORT_OK );
@EXPORT_OK = qw( show_call_style );
use Class::OOorNO qw( OOorNO );
sub new { bless { }, shift }
sub show_call_style {
if (ref OOorNO(@_)) {
print __PACKAGE__ . "::foo was called as an OBJECT METHOD.\n"
}
elsif (OOorNO(@_)) {
print __PACKAGE__ . "::foo was called as an CLASS METHOD.\n"
}
else {
print __PACKAGE__ . "::foo was called as a SUBROUTINE.\n"
}
}
User's code...
package main;
use strict;
use Your::Module qw( show_call_style );
my($YM) = Your::Module->new;
$YM->show_call_style; # as an object method
Your::Module->show_call_style; # as a class method
&Your::Module::show_call_style; # as a subroutine
&show_call_style; # as imported subroutine
Output:
Your::Module::foo was called as an OBJECT METHOD.
Your::Module::foo was called as an CLASS METHOD.
Your::Module::foo was called as a SUBROUTINE.
Your::Module::foo was called as a SUBROUTINE.
using "myself()"
Your module...
package Your::Module;
use strict;
use Exporter;
use vars qw( @EXPORT_OK );
@EXPORT_OK = qw( print_self_name );
use Class::OOorNO qw( myself );
sub new { bless { }, shift }
sub print_self_name {
print( (ref myself(@_) || myself(@_) || __PACKAGE__), "\n" )
}
User's code...
package main;
use strict;
use Your::Module qw( print_self_name );
my($YM) = Your::Module->new;
$YM->print_self_name; # as an object method
Your::Module->print_self_name; # as a class method
&Your::Module::print_self_name; # as a subroutine
print_self_name; # as imported subroutine
Output:
Your::Module
Your::Module
Your::Module
Your::Module
Your module...
package Your::Module;
use strict;
use Exporter;
use vars qw( @EXPORT_OK );
@EXPORT_OK = qw( show_call_style get_self_ref );
use Class::OOorNO qw( OOorNO myself );
sub new { bless { }, shift }
sub show_call_style {
if (ref OOorNO(@_)) {
print __PACKAGE__ . "::foo was called as an OBJECT METHOD.\n"
}
elsif (OOorNO(@_)) {
print __PACKAGE__ . "::foo was called as an CLASS METHOD.\n"
}
else {
print __PACKAGE__ . "::foo was called as a SUBROUTINE.\n"
}
}
sub get_self_ref {
ref myself(@_) ? myself(@_) : __PACKAGE__->new
}
User's code...
package main;
use strict;
use Your::Module qw( show_call_style get_self_ref );
my($YM) = Your::Module->new;
# supports calls that go way down the stack too:
Your::Module->new->get_self_ref->show_call_style;
Your::Module->get_self_ref->show_call_style;
&Your::Module::get_self_ref->show_call_style;
get_self_ref->show_call_style;
Output:
Your::Module::foo was called as an OBJECT METHOD.
Your::Module::foo was called as an OBJECT METHOD.
Your::Module::foo was called as an OBJECT METHOD.
Your::Module::foo was called as an OBJECT METHOD.
using "myargs()"
Your module...
package Your::Module;
use strict;
use Exporter;
use vars qw( @EXPORT_OK );
@EXPORT_OK = qw( print_argument_list );
use Class::OOorNO qw( myargs );
sub new { bless { }, shift }
sub print_argument_list {
print "My argument list: \n" . join("\n", myargs(@_)), "\n";
}
User's code...
package main;
use strict;
use Your::Module qw( print_argument_list );
my($YM) = Your::Module->new;
my(@things) = ( 'foo',
12687.357,
$YM,
eval('*bar'),
[ 'baz', sub { "wubble" },
{ 'flarp' => 'wibble' } ] );
$YM->print_argument_list(@things); # as an object method
Your::Module->print_argument_list(@things); # as a class method
&Your::Module::print_argument_list(@things); # as a subroutine
print_argument_list(@things); # as imported subroutine
Output:
My argument list:
foo
12687.357
Your::Module=HASH(0x9bd858)
*main::bar
ARRAY(0x9bd954)
...repeated four times
using "coerce_array()"
Your module...
package Your::Module;
use strict;
use Exporter;
use vars qw( @EXPORT_OK );
@EXPORT_OK = qw( pass_name_value_pairs );
use Class::OOorNO qw( coerce_array );
sub new { bless { }, shift }
sub pass_name_value_pairs {
my($input) = coerce_array(@_);
my($driver) = $input->{'-driver'} || 'nobody';
my($car) = $input->{'-car'} || 'no car';
my($bike) = $input->{'-bike'} || 'no bike';
my($plane) = $input->{'-plane'} || 'no plane';
print("$driver drives $car, $bike, and $plane.\n");
}
User's code...
Output:
using "shave_opts()"
Your module...
package Your::Module;
use strict;
use Exporter;
use vars qw( @EXPORT_OK );
@EXPORT_OK = qw( print_options );
use Class::OOorNO qw( shave_opts );
sub new { bless { }, shift }
sub print_options {
my($opts) = shave_opts(\@_);
print "\n",
( map { qq[$_ => $opts->{$_}] . "\n" } keys %$opts ),
"\n"
}
User's code...
Output:
PREREQUISITES
None.
BUGS
This documentation isn't done yet, as you can see. This is being rectified as quickly as
possible. Please excercise caution if you choose to use this code before it can be
further documented for you. It is present on CPAN at this time despite its unfinished
condition in order to provide support for the File::Util module which lists Class::OOorNO
among its prerequisites. Please excuse the inconvenience.
AUTHOR
Tommy Butler <cpan@atrixnet.com <mailto:cpan@atrixnet.com>>
COPYRIGHT
Copyright(c) 2001-2003, Tommy Butler. All rights reserved.
LICENSE
This library is free software, you may redistribute and/or modify it under the same terms
as Perl itself.
SEE ALSO
Devel::Caller
Class::ParmList
Class::ParamParser
Exporter