Design Patterns in Ruby [Digest 11] Factory

Factory is used to integrate the creation of some related object into one responsory class:

class PondOrganismFactory
  def new_animal(name)
    Frog.new(name)
  end
  def new_plant(name)
    Algae.new(name)
  end
end

 

class JungleOrganismFactory
  def new_animal(name)
    Tiger.new(name)
  end
  def new_plant(name)
    Tree.new(name)
  end
end

 

 

In ruby the class is an object too, you can create factory by class name

 

class IOFactory
  def initialize(format)
    @reader_class = self.class.const_get("#{format}Reader")
    @writer_class = self.class.const_get("#{format}Writer")
  end

  def new_reader
    @reader_class.new
  end

  def new_writer
    @writer_class.new
  end
end

html_factory = IOFactory.new('HTML')
html_reader = html_factory.new_reader

pdf_factory = IOFactory.new('PDF')
pdf_writer = pdf_factory.new_writer