error = Error Domain=NSCocoaErrorDomain Code=3840

json解析，同样的请求，有一个请求，无反应。纠结了几天，终于解决了。

error = Error Domain=NSCocoaErrorDomain Code=3840 "Unescaped control character around character 168." UserInfo={NSDebugDescription=Unescaped control character around character 168.}

报错信息如上：

这个原因，是因为服务器返回的字符串里面有换行符，所以我们要在接收到的数据里面，将换行符替换掉，然后再转模型。

但是，AFN解析，并没有提供原有的数据给我们（我没找），就直接去了error 的接口。

然后用session的dataTask，用字符串转它返回的data，则能够把数据读取出来，打印，果然有换行符。于是，改写了原来的方法，用session去代替。

    NSString * url = infoCategoryM.listUrl;
    NSURL * URL = [NSURL URLWithString:url];
    NSURLRequest * request = [NSURLRequest requestWithURL:URL];
    NSURLSession * session = [NSURLSession sharedSession];
    NSURLSessionDataTask * dataTask = [session dataTaskWithRequest:request completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) {
        NSString * str = [[NSString alloc]initWithData:data encoding:NSUTF8StringEncoding];
        NSString * str2 = [str stringByReplacingOccurrencesOfString:@"\t" withString:@""];
        str2 = [str2 stringByReplacingOccurrencesOfString:@"\n" withString:@""];
        str2 = [str2 stringByReplacingOccurrencesOfString:@"\r" withString:@""];

        ContentListArrM * contentListArrM = [[ContentListArrM alloc]initWithString:str2 error:nil];
        [self.contentListArr removeAllObjects];
        for (int i = 0; i < contentListArrM.contentList.count ; i++) {
            ContentListM * m = [contentListArrM.contentList objectAtIndex:i];
            if (![XSDKResourceUtil xsdkstringIsnilOrEmpty:m.title]) {
                [self.contentListArr addObject:m];
            }
        }
        dispatch_async(dispatch_get_main_queue(), ^{
            [self.infoTableView reloadData];
            self.selectedButton.selected = NO;
            selectedButton.selected = YES;
            self.selectedButton = selectedButton;
            NewsTableViewCell * cell = [self.infoTableView cellForRowAtIndexPath:[NSIndexPath indexPathForRow:1 inSection:0]];
            cell.selected = YES;
        });

    }];
    [dataTask resume];

　　里面，替换掉了换行符等其他字符，然后再转模型。

This application is modifying the autolayout engine from a background thread, which can lead to engine corruption and weird crashes.  This will cause an exception in a future release.

这个错误，是告诉我们，要在主线程里面更新UI。