How do I count the number of words in a String in Swift?

Question

Say I have a String, how do I determine the number of words in it? I'm trying to create an extension like:

extension String {
    var numberOfWords: Int {
        // Insert string-counting code here
    }
}

Answer 1

If you search "word count string swift" you'll find dozens of StackOverflow answers and gists that tell you to split the string using str.components(separatedBy: " ").count.

DON'T USE components(separatedBy:)!!!

Many non-European languages (particularly East Asian languages) don't use spaces to split words. This will also incorrectly count hyphenated words as separate, and lone punctuation as a word.

The most correct AND most performant way to solve this problem is to use either enumerateSubstrings(in:options:) or CFStringTokenizer.

// enumerateSubstrings
extension String {
    var numberOfWords: Int {
        var count = 0
        let range = startIndex..<endIndex
        enumerateSubstrings(in: range, options: [.byWords, .substringNotRequired, .localized], { _, _, _, _ -> () in
            count += 1
        })
        return count
    }
}

OR:

// CFStringTokenizer
extension String {
    var numberOfWords: Int {
        let inputRange = CFRangeMake(0, utf16.count)
        let flag = UInt(kCFStringTokenizerUnitWord)
        let locale = CFLocaleCopyCurrent()
        let tokenizer = CFStringTokenizerCreate(kCFAllocatorDefault, self as CFString, inputRange, flag, locale)
        var tokenType = CFStringTokenizerAdvanceToNextToken(tokenizer)
        var count = 0
        
        while tokenType != [] {
            count += 1
            tokenType = CFStringTokenizerAdvanceToNextToken(tokenizer)
        }
        return count
    }
}

Both are very performant, but enumerateSubtrings(in:options:...) is about twice as fast.

Shocked that nobody is pointing this out elsewhere, so I hope people searching for a solution find this.