您可以使用String方法enumerateSubstringsInRange。第一个参数只是传递您的字符串Range<Index>和选项.byWords。只需将每个子字符串附加到结果集合中并返回即可。

Swift 5或更高版本 （对于较早的Swift语法，请检查编辑历史记录）

import Foundation

extension StringProtocol { // for Swift 4 you need to add the constrain `where Index == String.Index` 
    var byWords: [SubSequence] {
        var byWords: [SubSequence] = []
        enumerateSubstrings(in: startIndex..., options: .byWords) { _, range, _, _ in
            byWords.append(self[range])
        }
        return byWords
    }
}

用法：

let sentence = "Out of this world!!!"
let words = sentence.byWords             // ["Out", "of", "this", "world"]
let firstWord = words.first      // "Out"
let lastWord = words.last         // world"
let first2Words = words.prefix(2) // ["Out", "of"]
let last2Words = words.suffix(2)   // ["this", "world"]

无进口基金会

清洁标点符号过滤字符串中的字母和空格

let clean = sentence.filter{ $0.isLetter || $0.isWhitespace }

查找字符串中最后一个空格的索引

if let index = clean.lastIndex(of: " ") {
    let lastWord = clean[index...]
    print(lastWord)   // "world"
}

查找字符串中第一个空格的索引

if let index = clean.firstIndex(of: " ") {
    let firstWord = clean[...index]
    print(firstWord)  // "Out""
}