Proper way to handle path arguments in Ruby methods

gistfile1.rb

def callee(arg)
  path   = arg.path    if arg.respond_to?(:path)
  path ||= arg.to_path if arg.respond_to?(:to_path)
  path ||= arg.to_str  if arg.respond_to?(:to_str)
  raise "Invalid path `#{arg}`" unless path

  # ... do something with path
end

From revision-zero.org.