How to count words within a text string?

Question

On iOS, how can I count words within a specific text string?

Answer 1

A more efficient method than splitting is to check the string character by character.

int word_count(NSString* s) {
  CFCharacterSetRef alpha = CFCharacterSetGetPredefined(kCFCharacterSetAlphaNumeric);
  CFStringInlineBuffer buf;
  CFIndex len = CFStringGetLength((CFStringRef)s);
  CFStringInitInlineBuffer((CFStringRef)s, &buf, CFRangeMake(0, len));
  UniChar c;
  CFIndex i = 0;
  int word_count = 0;
  Boolean was_alpha = false, is_alpha;
  while (c = CFStringGetCharacterFromInlineBuffer(&buf, i++)) {
    is_alpha = CFCharacterSetIsCharacterMember(alpha, c);
    if (!is_alpha && was_alpha)
      ++ word_count;
    was_alpha = is_alpha;
  }
  if (is_alpha)
    ++ word_count;
  return word_count;
}

Compared with @ennuikiller's solution, counting a 1,000,000-word string takes:

• 0.19 seconds to build the string
• 0.39 seconds to build the string + counting using my method.
• 1.34 seconds to build the string + counting using ennuikiller's method.

The big disadvantage of my method is that it's not a one-liner.