physical_storage_volume.rb

class PhysicalStorageVolume
  OS_VERSION = RbConfig::CONFIG['host_os']

  def initialize(path)
    @path = path
    @path_exists = File.exists?(path)
  end
  
  def self.error_raising_method(name)
    define_method(name) do |*args|
      raise_error_if_file_doesnt_exist!
      yield(*args)
    end
  end

  def raise_error_if_file_doesnt_exist!
    raise Errno::ENOENT.new(@path) unless @path_exists
  end

  error_raising_method :uuid do
    @uuid ||= `diskutil info #{disk_name} | grep UUID`.split.last
  end

  error_raising_method :volume_label do
    unless @volume_label
      vname = 'Volume Name:'
      vname_line = `diskutil info #{disk_name} | grep '#{vname}'`
      @volume_label = vname_line.sub(vname, '').strip
    end
    @volume_label
  end
end