gistfile1.rb

#  Abstract classes, const_get etc examples for a dev friend

class String
  # http://github.com/rails/rails/blob/master/activesupport/lib/active_support/core_ext/string/inflections.rb#L44-49
  def camelize
    self.gsub(/\/(.?)/) { "::#{$1.upcase}" }.gsub(/(?:^|_)(.)/) { $1.upcase }
  end
end

module MyParsers

  def self.parse!(record={})
    parser = const_get( record[:parser].camelize ).new(record)
    parser.parse!
  end

  # Abstract class
  class Base
    def initialize(record)
      @url = record[:url]
    end
    def parse!
      raise NoMethodError, "Implement this, dude"
    end
  end

  class Xml < Base
    def parse!
      puts "Launching Nokogiri, eating ur XML at #{@url}"
    end
  end

  class SpecialXml < Xml
    def parse!
      puts "Launching Nokogiri, eating ur *** SPECIAL *** XML at #{@url}"
    end
  end

  class Json < Base
    def parse!
      puts "Launching yajl, eating ur JSON at #{@url}"
    end
  end
end

record_one = { :url => 'http://example.com/XML',  :parser => 'xml' }

record_two = { :url => 'http://example.com/JSON', :parser => 'json' }

record_three = { :url => 'http://example.com/JSON', :parser => 'special_xml' }



MyParsers.parse!(record_one)
MyParsers.parse!(record_two)
MyParsers.parse!(record_three)