AFNetWorking Failure Error

AFNetWorking 请求失败

AFNetWorking请求失败返回NSError分析，下面的方法是直接调用manager的post请求
- (nullable NSURLSessionDataTask *)POST:(NSString *)URLString
parameters:(nullable id)parameters
progress:(nullable void (^)(NSProgress *uploadProgress))uploadProgress
success:(nullable void (^)(NSURLSessionDataTask *task, id _Nullable responseObject))success
failure:(nullable void (^)(NSURLSessionDataTask * _Nullable task, NSError *error))failure;

在failure的block里打印error.userInfo和其keys

NSLog(@"***userInfo***:%@", error.userInfo);
NSLog(@"***userInfo.allKeys***:%@", error.userInfo.allKeys)；
2016-08-08 10:05:33.173 jmsfhz_ios[11475:4109574] ***userInfo.allKeys***:(
    NSDebugDescription,
    NSUnderlyingError
)

NSDebugDescription：该错误的描述
NSUnderlyingError：更加底层的错误，用字典方式取出后仍是一个NSError

下面再次打印这个底层error的userInfo的keys

NSLog(@"***underError.userInfo.allKeys***:%@", underError.userInfo.allKeys);
2016-08-08 10:05:33.194 jmsfhz_ios[11475:4109574] ***underError.userInfo.allKeys***:(
    "com.alamofire.serialization.response.error.response",
    NSErrorFailingURLKey,
    "com.alamofire.serialization.response.error.data",
    NSLocalizedDescription
)

"com.alamofire.serialization.response.error.response"：一个响应体数据
NSErrorFailingURLKey：失败的请求地址
"com.alamofire.serialization.response.error.data"：失败获取的数据，NSData类型，可以转化为字符串，获得它的描述
NSLocalizedDescription：错误描述