NAME
Pony::Object the object system.
OVERVIEW
Pony::Object is an object system, which provides simple way to use cute
objects.
SYNOPSIS
# Class: MyArticle
# Abstract class for articles.
package MyArticle;
use Pony::Object -abstract;
use MyArticle::Exception::IO; # Based on Pony::Object::Throwable class.
protected date => undef;
protected authors => [];
public title => '';
public text => '';
# Function: init
# Constructor.
# Parameters:
# date -- Integer
# authors -- ArrayRef
sub init : Public
{
my $this = shift;
($this->date, $this->authors) = @_;
}
# Function: getDate
# Get formatted date.
# Returns:
# String
sub getDate : Public
{
my $this = shift;
return $this->dateFormat($this->date);
}
# Function: dateFormat
# Convert Unix time to good looking string. Not implemented.
# Parameters:
# date -- Integer
# Returns:
# String
sub dateFormat : Abstract;
# Function: fromPdf
# Trying to create article from pdf file.
# Parameters:
# file -- String -- pdf file.
sub fromPdf : Public
{
my $this = shift;
my $file = shift;
try
{
open F, $file or
throw MyArticle::Exception::IO(action => "read", file => $file);
# do smth
close F;
}
catch
{
my $e = shift; # get exception object
if ($e->isa('MyArticle::Exception::IO'))
{
# handler for MyArticle::Exception::IO exceptions
}
};
}
1;
DESCRIPTION
When some package uses Pony::Object, it's becomes strict (and shows
warnings) and modern (can use perl 5.10 features like as "say"). Also
"dump" function is redefined and shows data structure. It's useful for
debugging.
Specific moments
Besides new function "dump" Pony::Object has other specific moments.
has
Keyword "has" declares new fields. All fields are public. You can also
describe object methods via "has"... If you want.
package News;
use Pony::Object;
# Fields
has 'title';
has text => '';
has authors => [ qw/Alice Bob/ ];
# Methods
sub printTitle
{
my $this = shift;
say $this->title;
}
sub printAuthors
{
my $this = shift;
print @{ $this->authors };
}
1;
package main;
my $news = new News;
$news->printAuthors();
$news->title = 'Something important';
$news->printTitle();
Pony::Object fields assigned via "=". For example: $obj->field = 'a'.
new
Pony::Object doesn't have method "new". In fact, of course it has. But
"new" is an internal function, so you should not use it if you want not
have additional fun. Instead of this Pony::Object has "init" function,
where you can write the same, what you wish write in "new". "init" is
after-hook for "new".
package News;
use Pony::Object;
has title => undef;
has lower => undef;
sub init
{
my $this = shift;
$this->title = shift;
$this->lower = lc $this->title;
}
1;
package main;
my $news = new News('Big Event!');
print $news->lower;
ALL
If you wanna get all default values of Pony::Object-based class (fields,
of course), you can call "ALL" method. I don't know why you need them,
but you can do it.
package News;
use Pony::Object;
has 'title';
has text => '';
has authors => [ qw/Alice Bob/ ];
1;
package main;
my $news = new News;
print for keys %{ $news->ALL() };
META
One more internal method. It provides access to special hash %META. You
can use it for Pony::Object introspection but do not trust it. It can be
changed in next versions.
my $news = new News;
say dump $news->META;
toHash
Get object's data structure and return it in hash.
package News;
use Pony::Object;
has title => 'World';
has text => 'Hello';
1;
package main;
my $news = new News;
print $news->toHash()->{text};
print $news->toHash()->{title};
dump
Return string which shows object current struct.
package News;
use Pony::Object;
has title => 'World';
has text => 'Hello';
1;
package main;
my $news = new News;
$news->text = 'Hi';
print $news->dump();
Returns
$VAR1 = bless( {
'text' => 'Hi',
'title' => 'World'
}, 'News' );
protected, private properties
For properties you can use "has" keyword if your variable starts with _
(for protected) or __ (for private).
package News;
use Pony::Object;
has text => '';
has __authors => [ qw/Alice Bob/ ];
sub getAuthorString
{
my $this = shift;
return join(' ', @{ $this->__authors });
}
1;
package main;
my $news = new News;
say $news->getAuthorString();
Or the same but with keywords "public", "protected" and "private".
package News;
use Pony::Object;
public text => '';
private authors => [ qw/Alice Bob/ ];
sub getAuthorString
{
my $this = shift;
return join(' ', @{ $this->authors });
}
1;
package main;
my $news = new News;
say $news->getAuthorString();
protected, private method
To define access for methods you can use attributes "Public", "Private"
and "Protected".
package News;
use Pony::Object;
public text => '';
private authors => [ qw/Alice Bob/ ];
sub getAuthorString : Public
{
return shift->joinAuthors(', ');
}
sub joinAuthors : Private
{
my $this = shift;
my $delim = shift;
return join( $delim, @{ $this->authors } );
}
1;
package main;
my $news = new News;
say $news->getAuthorString();
Inheritance
To define base classes you should set them as params on Pony::Object
use. For example, use Pony::Object 'Base::Class';
package FirstPonyClass;
use Pony::Object;
# properties
has a => 'a';
has d => 'd';
# method
has b => sub
{
my $this = shift;
$this->a = 'b';
return ( @_ ?
shift:
'b' );
};
# traditional perl method
sub c { 'c' }
1;
package SecondPonyClass;
# extends FirstPonyClass
use Pony::Object qw/FirstPonyClass/;
# Redefine property.
has d => 'dd';
# Redefine method.
has b => sub
{
my $this = shift;
$this->a = 'bb';
return ( @_ ?
shift:
'bb' );
};
# New method.
has e => sub {'e'};
1;
Singletons
For singletons Pony::Object has simple syntax. You just should declare
that on use Pony::Object;
package Notes;
use Pony::Object 'singleton';
has list => [];
sub add
{
my $this = shift;
push @{ $this->list }, @_;
}
sub flush
{
my $this = shift;
$this->list = [];
}
1;
package main;
use Notes;
my $n1 = new Notes;
my $n2 = new Notes;
$n1->add( qw/eat sleep/ );
$n1->add( 'Meet with Mary at 8 o`clock' );
$n2->flush;
# Em... When I must meet Mary?
Abstract methods and classes
You can use use abstract methods and classes in the following way:
# Let's define simple interface for texts.
package Text::Interface;
use Pony::Object -abstract; # Use 'abstract' or '-abstract'
# params to define abstract class.
sub getText : Abstract; # Use 'Abstract' attribute to
sub setText : Abstract; # define abstract method.
1;
# Now we can define base class for texts.
# It's abstract too but now it has some code.
package Text::Base;
use Pony::Object abstract => 'Text::Interface';
protected text => '';
sub getText : Public
{
my $this = shift;
return $this->text;
}
1;
# And in the end we can write Text class.
package Text;
use Pony::Object 'Text::Base';
sub setText : Public
{
my $this = shift;
$this->text = shift;
}
1;
# Main file.
package main;
use Text;
use Text::Base;
my $text = new Text::Base; # Raises an error!
my $text = new Text;
$text->setText('some text');
print $text->getText(); # Returns 'some text';
Don't forget, that perl looking for function from left to right in list
of inheritance packages. You should define abstract classes in the end
of Pony::Object param list.
Exceptions
Wanna to use Pony exceptions in your code? There is nothing easier! Use
block "try" to wrap code with possible exceptions, block "catch" to
catch exceptions and "finally" to define code, which should be runned
after all.
When we talk about exceptions we mean special type of Perl's "die". Base
class for all pony-exceptions is Pony::Object::Throwable. It has one
method "throw". It should be used on exceptions in the program.
try {
open F, $file or
throw Pony::Object::Throwable("Can't find $file.");
}
catch {
my $e = shift; # get exception object
say "Exception catched!";
say $e->dump();
# Let exception go to next catch block.
die $e;
};
SEE
Discussion
<
http://lorcode.org/thread/2338>
Git <
https://github.com/h15/pony-object>
COPYRIGHT AND LICENSE
Copyright (C) 2011 - 2013, Georgy Bazhukov.
This program is free software, you can redistribute it and/or modify it
under the terms of the Artistic License version 2.0.
