网络请求中出现一些错误数字代表的含义

NS_ENUM(NSInteger)

{

NSURLErrorUnknown = -1,

NSURLErrorCancelled = -999,

NSURLErrorBadURL = -1000,

NSURLErrorTimedOut = -1001,

NSURLErrorUnsupportedURL = -1002,

NSURLErrorCannotFindHost = -1003,

NSURLErrorCannotConnectToHost = -1004,

NSURLErrorNetworkConnectionLost = -1005,

NSURLErrorDNSLookupFailed = -1006,

NSURLErrorHTTPTooManyRedirects = -1007,

NSURLErrorResourceUnavailable = -1008,

NSURLErrorNotConnectedToInternet = -1009,

NSURLErrorRedirectToNonExistentLocation = -1010,

NSURLErrorBadServerResponse = -1011,

NSURLErrorUserCancelledAuthentication = -1012,

NSURLErrorUserAuthenticationRequired = -1013,

NSURLErrorZeroByteResource = -1014,

NSURLErrorCannotDecodeRawData =             -1015,

NSURLErrorCannotDecodeContentData =         -1016,

NSURLErrorCannotParseResponse =             -1017,

NSURLErrorAppTransportSecurityRequiresSecureConnectionNS_ENUM_AVAILABLE(10_11,9_0) = -1022,

NSURLErrorFileDoesNotExist = -1100,

NSURLErrorFileIsDirectory = -1101,

NSURLErrorNoPermissionsToReadFile = -1102,

NSURLErrorDataLengthExceedsMaximumNS_ENUM_AVAILABLE(10_5,2_0) = -1103,

// SSL errors

NSURLErrorSecureConnectionFailed = -1200,

NSURLErrorServerCertificateHasBadDate = -1201,

NSURLErrorServerCertificateUntrusted = -1202,

NSURLErrorServerCertificateHasUnknownRoot = -1203,

NSURLErrorServerCertificateNotYetValid = -1204,

NSURLErrorClientCertificateRejected = -1205,

NSURLErrorClientCertificateRequired = -1206,

NSURLErrorCannotLoadFromNetwork = -2000,

// Download and file I/O errors

NSURLErrorCannotCreateFile = -3000,

NSURLErrorCannotOpenFile = -3001,

NSURLErrorCannotCloseFile = -3002,

NSURLErrorCannotWriteToFile = -3003,

NSURLErrorCannotRemoveFile = -3004,

NSURLErrorCannotMoveFile = -3005,

NSURLErrorDownloadDecodingFailedMidStream = -3006,

NSURLErrorDownloadDecodingFailedToComplete =-3007,

NSURLErrorInternationalRoamingOffNS_ENUM_AVAILABLE(10_7,3_0) =         -1018,

NSURLErrorCallIsActiveNS_ENUM_AVAILABLE(10_7,3_0) =                    -1019,

NSURLErrorDataNotAllowedNS_ENUM_AVAILABLE(10_7,3_0) =                  -1020,

NSURLErrorRequestBodyStreamExhaustedNS_ENUM_AVAILABLE(10_7,3_0) =      -1021,

NSURLErrorBackgroundSessionRequiresSharedContainerNS_ENUM_AVAILABLE(10_10,8_0) = -995,

NSURLErrorBackgroundSessionInUseByAnotherProcessNS_ENUM_AVAILABLE(10_10,8_0) = -996,

NSURLErrorBackgroundSessionWasDisconnectedNS_ENUM_AVAILABLE(10_10,8_0)= -997,

};