case-refactor1.rb

HTMLFormatter = lambda { |data| "<p>#{data}</p>" }
TextFormatter = lambda { |data| data }
PDFFormatter  = lambda { |data| "<pdf>#{data}</pdf" }

def output(data, format)
  case format
  when :html
    return HTMLFormatter.call(data)
  when :text
    return TextFormatter.call(data)
  when :pdf
    return PDFFormatter.call(data)
  else
    raise ArgumentError, "Invalid format (#{format})."
  end
end