Error
最近在修改一个网络请求的
bug时，由于一直请求失败，所以在寻找具体失败原因的时候，了解了一下请求失败的错误返回NSError，发现原来可以通过NSError中的code属性来判断请求失败的具体原因，就在这里记录顺便分享一下。
判断方法
通过判断 NSError 中的 code 错误码属性，可以判断具体失败原因，下面以 NSURLErrorTimedOut 请求超时为例。
/* 开始请求 */
[manager POST:url parameters:parameters progress:nil success:^(NSURLSessionDataTask * _Nonnull task, id _Nullable responseObject) {
NSLog(@"网络请求成功！");
} failure:^(NSURLSessionDataTask * _Nullable task, NSError * _Nonnull error) {
NSLog(@"网络请求失败！");
if (error.code == NSURLErrorTimedOut) {
NSLog(@"网络请求超时！");
}
}];
错误码
这里给出苹果提供的所有网络请求的错误码，可以根据不同错误码来给出不同的错误提示以及给出相应的操作，想具体了解每个错误码对应什么意思可以自行查询一下官方文档。
/*!
@enum NSURL-related Error Codes
@abstract Constants used by NSError to indicate errors in the NSURL domain
*/
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,
NSURLErrorAppTransportSecurityRequiresSecureConnection NS_ENUM_AVAILABLE(10_11, 9_0) = -1022,
NSURLErrorFileDoesNotExist = -1100,
NSURLErrorFileIsDirectory = -1101,
NSURLErrorNoPermissionsToReadFile = -1102,
NSURLErrorDataLengthExceedsMaximum NS_ENUM_AVAILABLE(10_5, 2_0) = -1103,
NSURLErrorFileOutsideSafeArea API_AVAILABLE(macosx(10.12.4), ios(10.3), watchos(3.2), tvos(10.2)) = -1104,
// 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,
NSURLErrorInternationalRoamingOff NS_ENUM_AVAILABLE(10_7, 3_0) = -1018,
NSURLErrorCallIsActive NS_ENUM_AVAILABLE(10_7, 3_0) = -1019,
NSURLErrorDataNotAllowed NS_ENUM_AVAILABLE(10_7, 3_0) = -1020,
NSURLErrorRequestBodyStreamExhausted NS_ENUM_AVAILABLE(10_7, 3_0) = -1021,
NSURLErrorBackgroundSessionRequiresSharedContainer NS_ENUM_AVAILABLE(10_10, 8_0) = -995,
NSURLErrorBackgroundSessionInUseByAnotherProcess NS_ENUM_AVAILABLE(10_10, 8_0) = -996,
NSURLErrorBackgroundSessionWasDisconnected NS_ENUM_AVAILABLE(10_10, 8_0)= -997,
};
其实
NSError还有很多别的错误码，这里只给出网络请求相关的，其他的以后遇到了再记录下来吧。
将来的你，一定会感激现在拼命的自己，愿自己与读者的开发之路无限美好。
