gistfile1.rb

class Doc
  class Base
    def read; end
    def destroy!; end
  end

  class File < Base
    # operates on a file
  end

  class DestroyedDoc < Base
    # raises errors
  end

  class Proxy < Base
    def initialize(doc)
      @doc = doc
    end

    def destroy!
      @doc.destroy!
      @doc = Doc::DestroyedDoc.new(path)
    end

    def read
      @doc.read
    end
  end

  def self.open(path)
    Doc::Proxy.new(Doc::File.new(path))
  end
end