registry

registry is used to mix into a super class that has many or multiple implementations via subclasses.

This has been described to me as a factory pattern, John Barton describes 'registry' as a "metaprogrammed method factory".

A good example of this is a parser, you might have a parser for json and another for yml. Register your sub classes to handle certain labels or descriptions, then let the super class decide weather the message you send it can be handled or not.

Usage

A simple set of parsers:

require 'registry'

class Parser
  extend Registry
end

class Json < Parser
  identifier :json, :javascript

  def self.parse
    puts "parsing json..."
  end
end

class Yaml < Parser
  def self.parse
    puts "parsing yaml..."
  end
end

Look for your the json parser

Parser.for(:json).parse

Or the Yaml parser. Notice it also uses its class name as an identifier

Parser.for(:yaml).parse(items)

There is no parser for XML, this will raise a Registry::NotRegistered exception

Parser.for(:xml).parse(items)

Perhaps you'd like to call methods on the matching parser with a block? You can!

Parser.for(:json) do
  parse(feed)
end

Installation

gem install registry --source http://gemcutter.org

Note on Patches/Pull Requests

• Fork the project.
• Make your feature addition or bug fix.
• Add tests for it. This is important so I don't break it in a future version unintentionally.
• Commit, do not mess with rakefile, version, or history. (if you want to have your own version, that is fine but bump version in a commit by itself I can ignore when I pull)
• Send me a pull request. Bonus points for topic branches.

Copyright

Copyright (c) 2009 Ben Schwarz. See LICENSE for details.