case-refactor2.rb

# Lambda's are used here for simplicity. In reality each formatter would 
# probably be a separate class.
FORMATTERS = {
  :html => lambda { |data| "<p>#{data}</p>" },
  :text => lambda { |data| data },
  :pdf  => lambda { |data| "<pdf>#{data}</pdf>" }
}

def output(data, format)
  raise ArgumentError, 
    "Invalid format (#{format})." unless FORMATTERS.has_key?(format)

  FORMATTERS.fetch(format).call(data)
end