def enum_by_name(name)
      Enumerator.new(self, Proc.new { |field| field.name?(name) })
    end
def enum_by_name(name)
      Enumerator.new(self, Proc.new { |field| field.name?(name) })
    end
Returns an Enumerator for each Field for which #name?(+name+) is true.

 An Enumerator supports all the methods of Enumerable, so it allows iteration,
 collection, mapping, etc.

 Examples:

 Print all the nicknames in a card:

   card.enum_by_name("NICKNAME") { |f| puts f.value }

 Print an Array of the preferred email addresses in the card:

   pref_emails = card.enum_by_name("EMAIL").select { |f| f.pref? }