【iOS】判断字符串是否是url及从字符串中提取url

　　1、判断字符串是否是url

- (BOOL)checkUrlWithString:(NSString *)url {
    if(url.length < 1)
        return NO;
    if (url.length>4 && [[url substringToIndex:4] isEqualToString:@"www."]) {
        url = [NSString stringWithFormat:@"http://%@",url];
    } else {
        url = url;
    }
    NSString *urlRegex = @"(https|http|ftp|rtsp|igmp|file|rtspt|rtspu)://((((25[0-5]|2[0-4]\d|1?\d?\d)\.){3}(25[0-5]|2[0-4]\d|1?\d?\d))|([0-9a-z_!~*'()-]*\.?))([0-9a-z][0-9a-z-]{0,61})?[0-9a-z]\.([a-z]{2,6})(:[0-9]{1,4})?([a-zA-Z/?_=]*)\.\w{1,5}";

    NSPredicate* urlTest = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", urlRegex];

    return [urlTest evaluateWithObject:url];
}

　　2、提取url

- (NSArray*)getURLFromStr:(NSString *)string {
    NSError *error;
    //可以识别url的正则表达式
    NSString *regulaStr = @"((http[s]{0,1}|ftp)://[a-zA-Z0-9\.\-]+\.([a-zA-Z]{2,4})(:\d+)?(/[a-zA-Z0-9\.\-~!@#$%^&*+?:_/=<>]*)?)|(www.[a-zA-Z0-9\.\-]+\.([a-zA-Z]{2,4})(:\d+)?(/[a-zA-Z0-9\.\-~!@#$%^&*+?:_/=<>]*)?)";

    NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:regulaStr
    options:NSRegularExpressionCaseInsensitive
    error:&error];

    NSArray *arrayOfAllMatches = [regex matchesInString:string
    options:0
    range:NSMakeRange(0, [string length])];

    //NSString *subStr;
    NSMutableArray *arr=[[NSMutableArray alloc] init];

    for (NSTextCheckingResult *match in arrayOfAllMatches){
        NSString* substringForMatch;
        substringForMatch = [string substringWithRange:match.range];
        [arr addObject:substringForMatch];
    }
    return arr;
}

　　3、swift版的检测是否包含url

 let isHasUrl = false
let regularRange = NSRange(location: 0, length: messageLabel.text!.utf16.count)
            if let detector = try? NSDataDetector(types: NSTextCheckingResult.CheckingType.link.rawValue) {
                var isHasUrl = false
                detector.enumerateMatches(in: messageLabel.text!, options: [], range: regularRange) { (textCheckingResult, falgs, nil) in
                    if ((textCheckingResult?.url) != nil) {
                        isHasUrl = true
                    }
                }
            }

　　注：使用swift版本这个，获取字符串中的url时，容易出现奇怪的编码，所有只做检测，没做提取字符串。