func tokenize(text: String) { let tokenizer = NLTokenizer(unit: .word) tokenizer.string = text let tokens = tokenizer.tokens(for: text.startIndex ..< text.endIndex) var textTokens: [String] = [] for token in tokens { let tokenStartI = token.lowerBound let tokenEndI = token.upperBound let text = text[tokenStartI ..< tokenEndI] textTokens.append(String(text)) } print(textTokens) }