.characters deprecated? From Listing 7.4

Swift Programming: The Big Nerd Ranch Guide (2nd E 7. Strings
1

Latest XCODE marks the .characters as deprecated, from Listing 7.4. Could use some help understanding how the implementation should work in XCODE 8.4.1. Thanks.

2

Going to the on line reference manual at swift.org I found that

for c: Character in mutablePlayground {
print("‘©’")
}

works

3

characters’ is deprecated: Please use String or Substring directly

and my print The results of ：
print(“aAcute:(aAcute.characters.count); aAcutePrecomposed :(aAcutePrecomposed.characters.count)”);//aAcute:1;AacutePrecomposed :2
maybe my computer broken…
What should I do