AFNetworking 关于JSON text did not start with array or object and option to allow fragments not set 错误

AFHTTPSessionManager *manager =[AFHTTPSessionManager manager];
    [manager GET:@"http://www.baidu.com" parameters:nil success:^(NSURLSessionDataTask *task, id responseObject) {
        NSString *result = [[NSString alloc]initWithData:responseObject encoding:NSUTF8StringEncoding];
        NSLog(@"%@",result);
    } failure:^(NSURLSessionDataTask *task, NSError *error) {
        NSLog(@"%@",error);
    }];

在AFNetworking中 上述代码将会 输出

Error Domain=NSCocoaErrorDomain Code=3840 "The operation couldn’t be completed. (Cocoa error 3840.)" (JSON text did not start with array or object and option to allow fragments not set.) UserInfo=0x8ea19a0 {NSDebugDescription=JSON text did not start with array or object and option to allow fragments not set.}

这是因为 AFNetworking默认把响应结果当成json来处理,(默认manager.responseSerializer = [AFJSONResponseSerializer serializer]) ,很显然,我们请求的百度首页 返回的并不是一个json文本,而是一个html网页,但是AFNetworking并不知道,它坚信请求的结果就是一个json文本!然后固执地以json的形式去解析,显然没办法把一个网页解析成一个字典或者数组,所以产生了上述错误.

然而,我们期望它能够正确地处理这个情形,而不是提示一个错误. 
这时候 你必须告诉AFNetworking:别把这个网页当json来处理! 
只需要在发送请求前加入:manager.responseSerializer = [AFHTTPResponseSerializer serializer]

代码变成:

    AFHTTPSessionManager *manager =[AFHTTPSessionManager manager];
    manager.responseSerializer = [AFHTTPResponseSerializer serializer];
    [manager GET:@"http://www.baidu.com" parameters:nil success:^(NSURLSessionDataTask *task, id responseObject) {
        NSString *result = [[NSString alloc]initWithData:responseObject encoding:NSUTF8StringEncoding];
        NSLog(@"%@",result);
    } failure:^(NSURLSessionDataTask *task, NSError *error) {
        NSLog(@"%@",error);
    }];

 

这样,就可以正确地把baidu.com首页的html源码抓回来啦.