Objective-C: -[NSString wordCount]

Question

What\'s a simple implementation of the following NSString category method that returns the number of words in self, where words are separated by an

Answer 1

Looks like the second link I gave in my question still reigns as not only the fastest but also, in hindsight, a relatively simple implementation of -[NSString wordCount].

Answer 2

A Objective-C one-liner version

NSInteger wordCount = word ? ([word stringByTrimmingCharactersInSet:NSCharacterSet.whitespaceAndNewlineCharacterSet.invertedSet].length + 1) : 0;

Answer 3

- (NSUInteger) wordCount
{
   NSArray *words = [self componentsSeparatedByString:@" "];
   return [words count];
}

Answer 4

I believe you have identified the 'simplest'. Nevertheless, to answer to your original question - "a simple implementation of the following NSString category...", and have it posted directly here for posterity:

@implementation NSString (GSBString)

- (NSUInteger)wordCount
{
    __block int words = 0;
    [self enumerateSubstringsInRange:NSMakeRange(0,self.length)
                             options:NSStringEnumerationByWords
                          usingBlock:^(NSString *substring, NSRange substringRange, NSRange enclosingRange, BOOL *stop) {words++;}];
    return words;
}

@end

Answer 5

There are a number of simpler implementations, but they all have tradeoffs. For example, Cocoa (but not Cocoa Touch) has word-counting baked in:

- (NSUInteger)wordCount {
    return [[NSSpellChecker sharedSpellChecker] countWordsInString:self language:nil];
}

It's also trivial to count words as accurately as the scanner simply using [[self componentsSeparatedByCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]] count]. But I've found the performance of that method degrades a lot for longer strings.

So it depends on the tradeoffs you want to make. I've found the absolute fastest is just to go straight-up ICU. If you want simplest, using existing code is probably simpler than writing any code at all.

Answer 6

Why not just do the following?

- (NSUInteger)wordCount {
    NSCharacterSet *separators = [NSCharacterSet whitespaceAndNewlineCharacterSet];
    NSArray *words = [self componentsSeparatedByCharactersInSet:separators];

    NSIndexSet *separatorIndexes = [words indexesOfObjectsPassingTest:^BOOL(id obj, NSUInteger idx, BOOL *stop) {
        return [obj isEqualToString:@""];
    }];

    return [words count] - [separatorIndexes count];
}