Multion pattern

test.rb

# Multiton pattern
# extension to the Singleton pattern which maps unique keys to specific instances of a class. The idea is that there should only be one instance of an object for each unique key in use, limiting the number of objects that need to be created

class Font
  class << self
    def file_names
      @file_names ||= {}
    end
    
    def instances
      @instances ||= {}
    end
    
    def map(params)
      file_names.update(params)
    end
    
    def [](name)
      instances[name] ||= new(file_names[name])
    end
  end
  
  def initialize(filename)
    puts "Processing #{filename}"
  end
  
end

Font.map("Times New Roman" => "/path/to/times.ttf")

Font["Times New Roman"] #=> A font instance

p Font.file_names.inspect