万能公式，想得到什么数字就能得到什么数字

 NSString *string = @"测试sting14fkj测试5";    NSMutableArray *mutArr = [[NSMutableArray alloc] init];    for (int i = 0; i<string.length; i++)    {                NSString  *instanceStr = [string substringWithRange:NSMakeRange(i, 1)];        NSLog(@"instance:%@",instanceStr);        NSString  *regexStr = @"[0-9]";                NSPredicate *regex = [NSPredicate predicateWithFormat:@"SELF MATCHES %@",regexStr];        if ([regex evaluateWithObject:instanceStr])        {            NSLog(@"%@",instanceStr);            [mutArr addObject:instanceStr];        }        NSLog(@"%@",mutArr);    }