NSRegularExpressionenumerateMatchesInString 多次调用时挂起

使用 NSRegularExpression:enumerateMatchesInString 方法多次调用时，可能会导致程序挂起。这个方法是用于在给定的字符串中搜索匹配特定正则表达式模式的子字符串，并对这些子字符串进行处理。然而，如果字符串非常大，或者正则表达式的模式非常复杂，多次调用这个方法可能会导致程序变得非常缓慢甚至挂起。

swift
let inputString = "Hello, Swift! This is a test string. I want to find all the words that start with the letter 'S'. Let's see if NSRegularExpression can help us."
let pattern = "\\b[Ss]\\w+\\b"
let regex = try! NSRegularExpression(pattern: pattern, options: [])
regex.enumerateMatches(in: inputString, options: [], range: NSRange(inputString.startIndex..., in: inputString)) { (match, _, _) in
    if let match = match, let range = Range(match.range, in: inputString) {
        let word = inputString[range]
        print(word)
    }
}

swift
let inputString = "Hello, Swift! This is a test string. I want to find all the words that start with the letter 'S'. Let's see if NSRegularExpression can help us."
let pattern = "\\b[Ss]\\w+\\b"
let regex = try! NSRegularExpression(pattern: pattern, options: [])
DispatchQueue.global(qos: .background).async {
    regex.enumerateMatches(in: inputString, options: [], range: NSRange(inputString.startIndex..., in: inputString)) { (match, _, _) in
        if let match = match, let range = Range(match.range, in: inputString) {
            let word = inputString[range]
            print(word)
        }
    }
    
    DispatchQueue.main.async {
        // 更新用户界面
    }
}