使用NSRegularExpression结果子串字符串的正确方法是什么？

import Foundation

let inputString = "Hello, World! This is a test string."
let pattern = "\\b\\w+\\b" // 匹配单词的正则表达式模式

do {
    let regex = try NSRegularExpression(pattern: pattern, options: [])
    let matches = regex.matches(in: inputString, options: [], range: NSRange(location: 0, length: inputString.utf16.count))
    
    for match in matches {
        let range = match.range(at: 0)
        if let swiftRange = Range(range, in: inputString) {
            let substring = inputString[swiftRange]
            print(substring)
        }
    }
} catch {
    print("Invalid regular expression pattern: \(error)")
}