正则中有（）使用方法

NSString* str = [[NSString alloc]initWithData:responseObject encoding:NSUTF8StringEncoding];

NSString *regex = @"\"stream_url\": \"(.+)\"";

NSError *error;

NSRegularExpression *regular = [NSRegularExpression regularExpressionWithPattern:regex

options:NSRegularExpressionCaseInsensitive error:&error];

// 对str字符串进行匹配

NSArray *matches = [regular matchesInString:str options:0 range:NSMakeRange(0, str.length)];

// 遍历匹配后的每一条记录

for (NSTextCheckingResult *match in matches) {

//                NSRange range = [match range]; //符合匹配规则的值

NSRange range = [match rangeAtIndex:1]; //取匹配规则内第一个()的值      以 ( 位置为次序

NSString *urlString = [str substringWithRange:range];

}