Object::Container - simple object container

Object-Container documentation Contained in the Object-Container distribution.

Index

Code Index:

NAME

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Object::Container - simple object container

SYNOPSIS

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    use Object::Container;

    # initialize container
    my $container = Object::Container->new;

    # register class
    $container->register('HTML::TreeBuilder');

    # register class with initializer
    $container->register('WWW::Mechanize', sub {
        my $mech = WWW::Mechanize->new( stack_depth => 1 );
        $mech->agent_alias('Windows IE 6');
        return $mech;
    });

    # get object
    my $mech = $container->get('WWW::Mechanize');

    # also available Singleton interface
    my $container = Object::Container->instance;

    # With singleton interface, you can use register/get method as class method
    Object::Container->register('WWW::Mechanize');
    my $mech = Object::Container->get('WWW::Mechanize');

    # Export singleton interface
    use Object::Container 'container';
    container->register('WWW::Mechanize');
    my $mech = container->get('WWW::Mechanize');
    my $mech = container('WWW::Mechanize'); # save as above

    # Subclassing singleton interface
    package MyContainer;
    use Object::Container '-base';

    register mech => sub { WWW::Mechanize->new };

    # use it
    use MyContainer 'con';

    con('mech')->get('http://example.com');

DESCRIPTION

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This module is a object container interface which supports both OO interface and Singleton interface.

If you want to use one module from several places, you might use Class::Singleton to access the module from any places. But you should subclass each modules to singletonize.

This module provide singleton container instead of module itself, so it is easy to singleton multiple classes.

Object::Registrar is a similar module to this. But Object::Container has also OO interface and supports lazy initializer. (describing below)

OO and Singleton interfaces

This module provide two interfaces: OO and Singleton.

OO interface is like this:

    my $container = Object::Container->new;

It is normal object oriented interface. And you can use multiple container at the same Time:

    my $container1 = Object::Container->new;
    my $container2 = Object::Container->new;

Singleton is also like this:

    my $container = Object::Container->instance;

instance method always returns singleton object. With this interface, you can 'register' and 'get' method as class method:

    Object::Container->register('WWW::Mechanize');
    my $mech = Object::Container->get('WWW::Mechanize');

When you want use multiple container with Singleton interface, you have to create subclass like this:

    MyContainer1->get('WWW::Mechanize');
    MyContainer2->get('WWW::Mechanize');

Singleton interface with EXPORT function for lazy people

If you are lazy person, and don't want to write something long code like:

    MyContainer->get('WWW::Mechanize');

This module provide export functions to shorten this. If you use your container with function name, the function will be exported and act as container:

    use MyContainer 'container';

    container->register(...);

    container->get(...);
    container(...);             # shortcut to ->get(...);

Subclassing singleton interface for lazy people

If you are lazy person, and don't want to write something long code in your subclass like:

    __PACKAGE__->register( ... );

Instead of above, this module provide subclassing interface. To do this, you need to write below code to subclass instead of use base.

    use Object::Container '-base';

And then you can register your object via DSL functions:

    register ua => sub { LWP::UserAgent->new };

lazy loading and resolve dependencies

The object that is registered by 'register' method is not initialized until calling 'get' method.

    Object::Container->register('WWW::Mechanize', sub { WWW::Mechanize->new }); # doesn't initialize here
    my $mech = Object::Container->get('WWW::Mechanize'); # initialize here

This feature helps you to create less resource and fast runtime script in case of lots of object registered.

And you can resolve dependencies between multiple modules with Singleton interface.

For example:

    Object::Container->register('HTTP::Cookies', sub { HTTP::Cookies->new( file => '/path/to/cookie.dat' ) });
    Object::Container->register('LWP::UserAgent', sub {
        my $cookies = Object::Container->get('HTTP::Cookies');
        LWP::UserAgent->new( cookie_jar => $cookies );
    });

You can resolve dependencies by calling 'get' method in initializer like above.

In that case, only LWP::UserAgent and HTTP::Cookies are initialized.

METHODS

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new

Create new object.

instance

Create singleton object and return it.

register( $class, @args )

register( $class_or_name, $initialize_code )

register( { class => $class_or_name ... } )

Register classes to container.

Most simple usage is:

    Object::Container->register('WWW::Mechanize');

First argument is class name to object. In this case, execute 'WWW::Mechanize->new' when first get method call.

    Object::Container->register('WWW::Mechanize', @args );

is also execute 'WWW::Mechanize->new(@args)'.

If you use different constructor from 'new', want to custom initializer, or want to include dependencies, you can custom initializer to pass a coderef as second argument.

    Object::Container->register('WWW::Mechanize', sub {
        my $mech = WWW::Mechanize->new( stack_depth );
        $mech->agent_alias('Windows IE 6');
        return $mech;
    });

This coderef (initialize) should return object to contain.

With last way you can pass any name to first argument instead of class name.

    Object::Container->register('ua1', sub { LWP::UserAgent->new });
    Object::Container->register('ua2', sub { LWP::UserAgent->new });

If you want to initialize and register at the same time, the following can.

    Object::Container->register({ class => 'LWP::UserAgent', preload => 1 });

initializer option can be specified.

    Object::Container->register({ class => 'WWW::Mechanize', initializer => sub {
        my $mech = WWW::Mechanize->new( stack_depth );
        $mech->agent_alias('Windows IE 6');
        return $mech;
    }, preload => 1 });

This is the same as written below.

    Object::Container->register('WWW::Mechanize', sub {
        my $mech = WWW::Mechanize->new( stack_depth );
        $mech->agent_alias('Windows IE 6');
        return $mech;
    });
    Object::Container->get('WWW::Mechanize');

If you specify args option is:

    Object::Container->register({ class => 'LWP::UserAgent', args => \@args, preload => 1 });

It is, as you know, the same below.

    Object::Container->register('LWP::UserAgent', @args);
    Object::Container->get('LWP::UserAgent');

unregister($class_or_name)

Unregister classes from container.

get($class_or_name)

Get the object that registered by 'register' method.

First argument is same as 'register' method.

remove($class_or_name)

Remove the cached object that is created at get method above.

Return value is the deleted object if it's exists.

ensure_class_loaded($class)

This is utility method that load $class if $class is not loaded.

It's useful when you want include dependency in initializer and want lazy load the modules.

load_all

load_all_except(@classes_or_names)

This module basically does lazy object initializations, but in some situation, for Copy-On-Write or for runtime speed for example, you might want to preload objects. For the purpose load_all and load_all_except method are exists.

    Object::Container->load_all;

This method is load all registered object at once.

Also if you have some objects that keeps lazy loading, do like following:

    Object::Container->load_all_except(qw/Foo Bar/);

This means all objects except 'Foo' and 'Bar' are loaded.

EXPORT FUNCTIONS ON SUBCLASS INTERFACE

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Same functions for load_all and load_all_except exists at subclass interface. Below is list of these functions.

preload(@classes_or_names)

preload_all

preload_all_except

As predictable by name, preload_all is equals to load_all and preload_all_except is equals to <load_all_except>.

SEE ALSO

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Class::Singleton, Object::Registrar.

AUTHOR

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Daisuke Murase <typester@cpan.org>

COPYRIGHT & LICENSE

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Copyright (c) 2009 KAYAC Inc. All rights reserved.

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

The full text of the license can be found in the LICENSE file included with this module.

Object-Container documentation Contained in the Object-Container distribution. 
package Object::Container;

use strict;
use warnings;
use parent qw(Class::Accessor::Fast);
use Carp;

our $VERSION = '0.14';

__PACKAGE__->mk_accessors(qw/registered_classes autoloader_rules objects/);

BEGIN {
    our $_HAVE_EAC = 1;
    eval { local $SIG{__DIE__}; require Exporter::AutoClean; };
    if ($@) {
        $_HAVE_EAC = 0;
    }    
}

do {
    my @EXPORTS;

    sub import {
        my ($class, $name) = @_;
        return unless $name;

        my $caller = caller;
        {
            no strict 'refs';
            if ($name =~ /^-base$/i) {
                push @{"${caller}::ISA"}, $class;
                my $r = $class->can('register');
                my $l = $class->can('autoloader');
    
                my %exports = (
                    register   => sub { $r->($caller, @_) },
                    autoloader => sub { $l->($caller, @_) },
                    preload    => sub {
                        $caller->instance->get($_) for @_;
                    },
                    preload_all_except => sub {
                        $caller->instance->load_all_except(@_);
                    },
                    preload_all => sub {
                        $caller->instance->load_all;
                    },
                );
    
                if ($Object::Container::_HAVE_EAC) {
                    Exporter::AutoClean->export( $caller, %exports );
                }
                else {
                    while (my ($name, $fn) = each %exports) {
                        *{"${caller}::${name}"} = $fn;
                    }
                    @EXPORTS = keys %exports;
                }
            }
            else {
                no strict 'refs';
                *{"${caller}::${name}"} = sub {
                    my ($target) = @_;
                    return $target ? $class->get($target) : $class;
                };
            }
        }
    }

    sub unimport {
        my $caller = caller;

        no strict 'refs';
        for my $name (@EXPORTS) {
            delete ${ $caller . '::' }{ $name };
        }

        1; # for EOF
    }
};

my %INSTANCES;
sub instance {
    my $class = shift;
    return $INSTANCES{$class} ||= $class->new;
}

sub has_instance {
    my $class = shift;
    $class = ref $class || $class;
    return $INSTANCES{$class};
};

sub new {
    $_[0]->SUPER::new( +{
        registered_classes => +{},
        autoloader_rules => +[],
        objects => +{},
    } );
}

sub register {
    my ($self, $args, @rest) = @_;
    $self = $self->instance unless ref $self;

    my ($class, $initializer, $is_preload);
    if (defined $args && !ref $args) {
        $class = $args;
        if (@rest == 1 and ref $rest[0] eq 'CODE') {
            $initializer = $rest[0];
        }
        else {
            $initializer = sub {
                $self->ensure_class_loaded($class);
                $class->new(@rest);
            };
        }
    }
    elsif (ref $args eq 'HASH') {
        $class = $args->{class};
        $args->{args} ||= [];
        if (ref $args->{initializer} eq 'CODE') {
            $initializer = $args->{initializer};
        }
        else {
            $initializer = sub {
                $self->ensure_class_loaded($class);
                $class->new(@{$args->{args}});
            };
        }

        $is_preload = 1 if $args->{preload};
    }
    else {
        croak "Usage: $self->register($class || { class => $class ... })";
    }

    $self->registered_classes->{$class} = $initializer;
    $self->get($class) if $is_preload;
    
    return $initializer;
}

sub unregister {
    my ($self, $class) = @_;
    $self = $self->instance unless ref $self;

    delete $self->registered_classes->{$class} and $self->remove($class);
}

sub autoloader {
    my ($self, $rule, $trigger) = @_;
    $self = $self->instance unless ref $self;

    push @{ $self->autoloader_rules }, [$rule, $trigger];
}

sub get {
    my ($self, $class) = @_;
    $self = $self->instance unless ref $self;

    my $obj = $self->objects->{ $class } ||= do {
        my $initializer = $self->registered_classes->{ $class };
        $initializer ? $initializer->($self) : ();
    };

    unless ($obj) {
        # autoloaderer
        if (my ($trigger) = grep { $class =~ /$_->[0]/ } @{ $self->autoloader_rules }) {
            $trigger->[1]->($self, $class);
        }

        $obj = $self->objects->{ $class } ||= do {
            my $initializer = $self->registered_classes->{ $class };
            $initializer ? $initializer->($self) : ();
        };        
    }
        
    $obj or croak qq["$class" is not registered in @{[ ref $self ]}];
}

sub remove {
    my ($self, $class) = @_;
    $self = $self->instance unless ref $self;
    delete $self->objects->{ $class };
}

sub load_all {
    my ($self) = @_;
    $self->load_all_except;
}

sub load_all_except {
    my ($self, @except) = @_;
    $self = $self->instance unless ref $self;

    for my $class (keys %{ $self->registered_classes }) {
        next if grep { $class eq $_ } @except;
        $self->get($class);
    }
}

# taken from Mouse
sub _is_class_loaded {
    my $class = shift;

    return 0 if ref($class) || !defined($class) || !length($class);

    # walk the symbol table tree to avoid autovififying
    # \*{${main::}{"Foo::"}{"Bar::"}} == \*main::Foo::Bar::

    my $pack = \%::;
    foreach my $part (split('::', $class)) {
        $part .= '::';
        return 0 if !exists $pack->{$part};

        my $entry = \$pack->{$part};
        return 0 if ref($entry) ne 'GLOB';
        $pack = *{$entry}{HASH};
    }

    return 0 if !%{$pack};

    # check for $VERSION or @ISA
    return 1 if exists $pack->{VERSION}
             && defined *{$pack->{VERSION}}{SCALAR} && defined ${ $pack->{VERSION} };
    return 1 if exists $pack->{ISA}
             && defined *{$pack->{ISA}}{ARRAY} && @{ $pack->{ISA} } != 0;

    # check for any method
    foreach my $name( keys %{$pack} ) {
        my $entry = \$pack->{$name};
        return 1 if ref($entry) ne 'GLOB' || defined *{$entry}{CODE};
    }

    # fail
    return 0;
}


sub _try_load_one_class {
    my $class = shift;

    return '' if _is_class_loaded($class);
    my $klass = $class;
    $klass  =~ s{::}{/}g;
    $klass .= '.pm';

    return do {
        local $@;
        eval { require $klass };
        $@;
    };
}

sub ensure_class_loaded {
    my ($self, $class) = @_;
    my $e = _try_load_one_class($class);
    Carp::confess "Could not load class ($class) because : $e" if $e;

    return $class;
}

1;
__END__


1;