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Simple-Factory-0.05
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/ Simple::Factory

NAME

Simple::Factory - a simple factory to create objects easily, with cache, autoderef and fallback supports

SYNOPSYS

use Simple::Factory;

my $factory = Simple::Factory->new(
    'My::Class' => {
        first  => { value => 1 },
        second => [ value => 2 ],
    },
    fallback => { value => undef }, # optional. in absent, will die if find no key
);

my $first  = $factory->resolve('first');  # will build a My::Class instance with arguments 'value => 1'
my $second = $factory->resolve('second'); # will build a My::Class instance with arguments 'value => 2'
my $last   = $factory->resolve('last');   # will build a My::Class instance with fallback arguments

DESCRIPTION

This is one way to implement the Factory Pattern. The main objective is substitute one hashref of objects ( or coderefs who can build/return objects ) by something more intelligent, who can support caching and fallbacks. If the creation rules are simple we can use Simple::Factory to help us to build instances.

We create instances with resolve method. It is lazy. If you need build all instances (to store in the cache) consider try to resolve them first.

If you need something more complex, consider some framework of Inversion of Control (IoC).

For example, we can create a simple factory to create DateTime objects, using CHI as cache:

 my $factory = Simple::Factory->new(
      build_class  => 'DateTime',
      build_method => 'from_epoch',
      build_conf   => {
          one      => { epoch => 1 },
          two      => { epoch => 2 },
          thousand => { epoch => 1000 }
      },
      fallback => sub { epoch => $_[0] }, # fallback can receive the key
      cache    => CHI->new( driver => 'Memory', global => 1),
  );

$factory->resolve( 1024 )->epoch # returns 1024

IMPORTANT: if the creation fails ( like some excetion from the constructor ), we will not call the fallback. We expect some error handling from your side.

ATTRIBUTES

build_class

Specify the perl package ( class ) used to create instances. Using Method::Runtime, will die if can't load the package.

This argument is required. You can omit by using the build_class as a first argument of the constructor.

build_args

Specify the mapping of key => arguments, storing in a hashref.

This argument is required. You can omit by using the build_class and build_args as a first pair of arguments.

Important: if autoderef is true, we will try to deref the value before use to create an instance.

fallback

The default behavior is die if we try to resolve an instance using one non-existing key.

But if fallback is present, we will use this on the constructor.

If autoderef is true and fallback is a code reference, we will call the code and pass the key as an argument.

build_method

By default the Simple::Factory calls the method new but you can override and specify your own build method.

Will croak if the build_class does not support the method on resolve.

autoderef

If true ( default ), we will try to deref the argument present in the build_conf only if it follow this rules:

  • will deref only references

  • if the reference is an array, we will call the build_method with @$array.

  • if the reference is a hash, we will call the build_method with %$hash.

  • if the reference is a scalar or other ref, we will call the build_method with $$ref.

  • if the reference is a glob, we will call the build_method with *$glob.

  • if the reference is a code, we will call the build_method with $code->( $key ) ( same thinf for the fallback )

  • other cases (like Regexes) we will carp if it is not in silence mode.

silence

If true ( default is false ), we will omit the carp message if we can't autoderef.

cache

If present, we will cache the result of the method resolve. The cache should responds to get, set and remove like CHI.

We will also cache fallback cases.

If we need add a new build_conf via add_build_conf_for, and override one existing configuration, we will remove it from the cache if possible.

default: not present

inline

Experimental feature. useful to create multiple inline definitions. See resolve.

This feature can change in the future.

on_error

Change the default behavior of what happens if build one instance throws on error.

Accepts a coderef. You can also use three initial shortcuts ( will be coerce to coderef ): croak, carp and fallback.

  • croak will croak the exception + extra message about the key ( default ).

  • carp will just carp instead croak and return undef.

  • fallback will resolve the fallback ( but in case of exception will die - to avoid one potential deadlock ).

Example:

my $factory = Simple::Factory->new(
    Foo => { ... },
    fallback => -1,
    on_error => "fallback" # in case of some exception, call the fallback
);

If one coderef was used, it will be called with one hashref as argument with three fields:

  • key with the value of the key

  • factory one reference for the factory itself

  • exception with the error message

Example:

my $factory =  Simple::Factory->new(
    Foo => { a => 1 },
    on_error => sub { $logger->warn("error while resolve key '$_[0]->{key}' : '$_[0]->{exception}'; undef },
);

$factory->resolve("b"); # will call 'on_error', log the exception and return undef

METHODS

add_build_conf_for

usage: add_build_conf_for( key => configuration [, options ])

Can add a new build configuration for one specific key. It is possible add new or just override.

You can change the behavior using an hash of options.

Options: you can avoid override one existing configuration with not_override and a true value.

Will remove cache if possible.

Example:

$factory->add_build_conf_for( last => { foo => 1, bar => 2 }); # can override
$factory->add_build_conf_for( last => { ... }, not_override => 1); # will croak instead override

resolve

usage: resolve( key [, keys ] )

The main method. Will build one instance of build_class using the build_conf and build_method.

Should receive a key and if does not exist a build_conf will try use the fallback if specified, or will die ( confess ).

If the cache attribute is present, will try to return first one object from the cache using the key, or will resolve and store in the cache for the next call.

You can pass multiple keys. If the instance responds to resolve method, we will call with the rest of the keys. It is useful for inline many factories.

Example:

my $factory = Simple::Factory->new(
    'Simple::Factory' => {
        Foo => {
            build_class => 'Foo',
            build_conf => {
                one => 1,
                two => 2,
            }
        },
        Bar => {
            Bar => {
                first => { ... },
                last => { ... },
            }
        }
    }
);

my $object = $factory->resolve('Foo', 'one'); # shortcut to ->resolve('Foo')->resolve('one');

Or, using inline experimental option.

my $factory = Simple::Factory->new(
    'Simple::Factory'=> {
        Foo => { one => 1, two => 2 },
        Bar => { first => 0, last => -1},
    },
    inline => 1,
);

If we have some exception when we try to create an instance for one particular key, we will not call the fallback. We use fallback when we can't find the build_conf based on the key.

get_fallback_for_key

this method will try to resolve the fallback. can be useful on on_error coderefs. accept the same argument as resolve.

SEE ALSO

Bread::Board

A solderless way to wire up your application components.

IOC

A lightweight IOC (Inversion of Control) framework

AUTHOR

Tiago Peczenyj <tiago (dot) peczenyj (at) gmail (dot) com>

BUGS

Please report any bugs or feature requests on the bugtracker website https://github.com/peczenyj/simple-factory-p5/issues