NAME Beam::Wire - A Dependency Injection Container VERSION version 0.011 SYNOPSIS # wire.yml dbh: class: 'DBI' method: connect args: - 'dbi:mysql:dbname' - { PrintError: 1 } # myscript.pl use Beam::Wire; my $wire = Beam::Wire->new( file => 'wire.yml' ); my $dbh = $wire->get( 'dbh' ); $wire->set( 'dbh' => DBI->new( 'dbi:pgsql:dbname' ) ); DESCRIPTION Beam::Wire is a dependency injection (DI) container. A DI (dependency injection) container is a framework/mechanism where dependency creation and instantiation is handled automatically (e.g. creates instances of classes that implement a given dependency interface on request). DI does not require a container, in-fact, DI without a container is possible and simply infers that dependency creation isn't automatically handled for you (i.e. you have to write code to instantiate the dependencies manually). Dependency injection (DI) at it's core is about creating loosely coupled code by separating construction logic from application logic. This is done by pushing the creation of services (dependencies) to the entry point(s) and writing the application logic so that dependencies are provided for its components. The application logic doesn't know or care how it is supplied with its dependencies; it just requires them and therefore receives them. OVERVIEW Beam::Wire loads a configuration file and stores the specified configuration in the config attribute which is used to resolve it's services. This section will give you an overview of how to declare dependencies and services, and shape your configuration file. WHAT IS A DEPENDENCY? A dependency is a declaration of a component requirement. In layman's terms, a dependency is a class attribute (or any value required for class construction) which will likely be used to define services. WHAT IS A SERVICE? A service is a resolvable interface which may be selected and implemented on behalf of a dependent component, or instantiated and returned per request. In layman's terms, a service is a class configuration which can be used independently or as a dependent of other services. HOW ARE SERVICES CONFIGURED? # databases.yml production_db: class: 'DBI' method: connect args: - 'dbi:mysql:master' - { PrintError: 0, RaiseError: 0 } production_cache: class: 'CHI' args: driver: 'DBI' dbh: { ref: 'production_db' } development_db: class: 'DBI' method: connect args: - 'dbi:mysql:slave' - { PrintError: 1, RaiseError: 1 } development_cache: class: 'CHI' args: driver: 'DBI' dbh: { ref: 'development_db' } Service Attributes class The class to instantiate. The class will be loaded and the "method" (below) method called. method The class method to call to construct the object. Defaults to "new". args The arguments to the "method" method. This can be either an array or a hash, like so: # array dbh: class: DBI method: connect args: - 'dbi:mysql:dbname' # hash cache: class: CHI args: driver: Memory max_size: 16MB Using the array of arguments, you can give arrayrefs or hashrefs: # arrayref of arrayrefs names: class: 'Set::CrossProduct' args: - - [ 'Foo', 'Barkowictz' ] - [ 'Bar', 'Foosmith' ] - [ 'Baz', 'Bazleton' ] # arrayrefs of hashrefs cache: class: CHI args: - driver: Memory max_size: 16MB extends Inherit and override attributes from another service. dbh: class: DBI method: connect args: - 'dbi:mysql:dbname' dbh_dev: extends: 'dbh' args: - 'dbi:mysql:devdb' Hash "args" will be merged seperately, like so: activemq: class: My::ActiveMQ args: host: example.com port: 61312 user: root password: 12345 activemq_dev: extends: 'activemq' args: host: dev.example.com "activemq_dev" will get the "port", "user", and "password" arguments from the base service "activemq". Inner Containers Beam::Wire objects can hold other Beam::Wire objects! inner: class: Beam::Wire args: config: dbh: class: DBI method: connect args: - 'dbi:mysql:dbname' cache: class: CHI args: driver: Memory max_size: 16MB Inner containers' contents can be reached from outer containers by separating the names with a slash character: my $dbh = $wire->get( 'inner/dbh' ); Inner Files inner: class: Beam::Wire args: file: inner.yml Inner containers can be created by reading files just like the main container. If the "file" attribute is relative, the parent's "dir" attribute will be added: # share/parent.yml inner: class: Beam::Wire args: file: inner.yml # share/inner.yml dbh: class: DBI method: connect args: - 'dbi:sqlite:data.db' # myscript.pl use Beam::Wire; my $container = Beam::Wire->new( file => 'share/parent.yml', ); my $dbh = $container->get( 'inner/dbh' ); If more control is needed, you can set the dir attribute on the parent container. If even more control is needed, you can make a subclass of Beam::Wire. Service/Configuration References chi: class: CHI args: driver: 'DBI' dbh: { ref: 'dbh' } dbh: class: DBI method: connect args: - { ref: dsn } - { ref: usr } - { ref: pwd } dsn: value: "dbi:SQLite:memory:" usr: value: "admin" pwd: value: "s3cret" The reuse of service and configuration containers as arguments for other services is encouraged so we have provided a means of referencing those objects within your configuration. A reference is an arugment (a service argument) in the form of a hashref with a "ref" key whose value is the name of another service. Optionally, this hashref may contain a "path" key whose value is a Data::DPath search string which should return the found data structure from within the referenced service. It is also possible to use raw-values as services, this is done by configuring a service using a single key/value pair with a "value" key whose value contains the raw-value you wish to reuse. ATTRIBUTES file The file attribute contains the file path of the file where Beam::Wire container services are configured (typically a YAML file). The file's contents should form a single hashref. The keys will become the service names. dir The dir attribute contains the directory path to use when searching for inner container files. Defaults to the directory which contains the file specified by the file attribute. config The config attribute contains a hashref of service configurations. This data is loaded by Config::Any using the file specified by the file attribute. services A hashref of services. If you have any services already built, add them here. METHODS get The get method resolves and returns the specified service. set The set method configures and stores the specified service. new Create a new container. AUTHORS * Doug Bell * Al Newkirk COPYRIGHT AND LICENSE This software is copyright (c) 2013 by Doug Bell. This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.