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)
":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>>
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