regex - 来自 URL 的 Youtube 视频 ID - Swift3

Question

基本上我有一个 Youtube URL 作为字符串，我想从该 URL 中提取视频 ID。我在 objective-c 中找到了一些代码，如下所示:

NSError *error = NULL;
NSRegularExpression *regex = 
[NSRegularExpression regularExpressionWithPattern:@"?.*v=([^&]+)"
                                          options:NSRegularExpressionCaseInsensitive
                                            error:&error];
NSTextCheckingResult *match = [regex firstMatchInString:youtubeURL
                                                options:0
                                                  range:NSMakeRange(0, [youtubeURL length])];
if (match) {
    NSRange videoIDRange = [match rangeAtIndex:1];
    NSString *substringForFirstMatch = [youtubeURL substringWithRange:videoIDRange];
}

当我将此代码转换为 swift3 时:

var error: Error? = nil
var regex = try! NSRegularExpression(pattern: "?.*v=([^&]+)", options: .caseInsensitive)
var match = regex!.firstMatch(in: youtubeURL, options: [], range: NSRange(location: 0, length: youtubeURL.length))!
if match {
    var videoIDRange = match.rangeAt(1)
    var substringForFirstMatch = (youtubeURL as NSString).substring(with: videoIDRange)
}

给出错误为:

fatal error: 'try!' expression unexpectedly raised an error: Error Domain=NSCocoaErrorDomain Code=2048 "The value “?.*v=([^&]+)” is invalid."

谁能帮我解决这个错误，或者谁能解释一下如何在 Swift 3 中从 url 获取视频 ID。

提前致谢

Answer 1

更安全版本(无需强制展开 !):

extension String {
    var youtubeID: String? {
        let pattern = "((?<=(v|V)/)|(?<=be/)|(?<=(\\?|\\&)v=)|(?<=embed/))([\\w-]++)"

        let regex = try? NSRegularExpression(pattern: pattern, options: .caseInsensitive)
        let range = NSRange(location: 0, length: count)

        guard let result = regex?.firstMatch(in: self, range: range) else {
            return nil
        }

        return (self as NSString).substring(with: result.range)
    }
}

例子:

"https://www.youtube.com/watch?v=C0DPdy98e4c".youtubeID // "C0DPdy98e4c"
"https://youtube.com/watch?v=C0DPdy98e4c".youtubeID // "C0DPdy98e4c"
"www.youtube.com/watch?v=C0DPdy98e4c".youtubeID // "C0DPdy98e4c"
"youtube.com/watch?v=C0DPdy98e4c".youtubeID // "C0DPdy98e4c"

"https://youtu.be/C0DPdy98e4c".youtubeID // "C0DPdy98e4c"
"youtu.be/C0DPdy98e4c".youtubeID // "C0DPdy98e4c"

致谢:Usman Nisar's answer