一、NSError是系统错误信息类
两种初始化方法：其中，domain 不能为空 dict可以为空
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- (instancetype)initWithDomain:(NSErrorDomain)domain code:(NSInteger)code userInfo:(nullable NSDictionary *)dict; + (instancetype)errorWithDomain:(NSErrorDomain)domain code:(NSInteger)code userInfo:(nullable NSDictionary *)dict; @property (readonly, copy) NSErrorDomain domain;//错误域 |
错误域主要有四个，对于Carbon框架的Error，归于OSStatus domain（NSOSStatusErrorDomain），对于POSIX error，归于NSPOSIXErrorDomain，而对于我们的iOS开发，一般使用NSCocoaErrorDomain。NSError.h定义了四个domain
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{ // Predefined domain for errors from most AppKit and Foundation APIs. FOUNDATION_EXPORT NSErrorDomain const NSCocoaErrorDomain; // Other predefined domains; value of "code" will correspond to preexisting values in these domains. FOUNDATION_EXPORT NSErrorDomain const NSPOSIXErrorDomain; FOUNDATION_EXPORT NSErrorDomain const NSOSStatusErrorDomain; FOUNDATION_EXPORT NSErrorDomain const NSMachErrorDomain; } @property (readonly) NSInteger code;//错误代码 @property (readonly, copy) NSDictionary *userInfo;//错误信息 @property (readonly, copy) NSString *localizedDescription;//获取本地化描述 @property (nullable, readonly, copy) NSString *localizedFailureReason;//获取失败原因 @property (nullable, readonly, copy) NSString *localizedRecoverySuggestion;//获取恢复建议 @property (nullable, readonly, copy) NSArray<NSString *> *localizedRecoveryOptions;本地恢复建议 @property (nullable, readonly, strong) id recoveryAttempter; @property (nullable, readonly, copy) NSString *helpAnchor; |
预定义的userinfo键名
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NSString *const NSUnderlyingErrorKey;//推荐的标准方式，通用键 NSString *const NSLocalizedDescriptionKey; // 详细描述键 NSString *const NSLocalizedFailureReasonErrorKey; // 失败原因键 NSString *const NSLocalizedRecoverySuggestionErrorKey; //恢复建议键 NSString *const NSLocalizedRecoveryOptionsErrorKey; // 恢复选项键 //其他键 NSString *const NSRecoveryAttempterErrorKey; NSString *const NSHelpAnchorErrorKey; NSString *const NSStringEncodingErrorKey ; NSString *const NSURLErrorKey; NSString *const NSFilePathErrorKey; |
用法示例：
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NSDictionary *userInfo1 = [NSDictionary dictionaryWithObjectsAndKeys:@"由于文件不存在，无法打开", NSLocalizedDescriptionKey, @"失败原因：文件不存在", NSLocalizedFailureReasonErrorKey, @"恢复建议：请创建该文件",NSLocalizedRecoverySuggestionErrorKey,nil]; NSError *error = [[NSError alloc] initWithDomain:NSCocoaErrorDomain code:4 userInfo:userInfo1]; |
此处code是4，对照下面对照表4代表文件不存在。userinfo传userinfo1 查看自定义打印。userinfo传nil，查看本地化描述。
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NSLog(@"========%@",[error localizedDescription]); NSLog(@"========%@",[error localizedFailureReason]); NSLog(@"========%@",[error localizedRecoverySuggestion]); |
二、NSError错误code对照表
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enum { NSFileNoSuchFileError = 4, NSFileLockingError = 255, NSFileReadUnknownError = 256, NSFileReadNoPermissionError = 257, NSFileReadInvalidFileNameError = 258, NSFileReadCorruptFileError = 259, NSFileReadNoSuchFileError = 260, NSFileReadInapplicableStringEncodingError = 261, NSFileReadUnsupportedSchemeError = 262, NSFileReadTooLargeError = 263, NSFileReadUnknownStringEncodingError = 264, NSFileWriteUnknownError = 512, NSFileWriteNoPermissionError = 513, NSFileWriteInvalidFileNameError = 514, NSFileWriteInapplicableStringEncodingError = 517, NSFileWriteUnsupportedSchemeError = 518, NSFileWriteOutOfSpaceError = 640, NSFileWriteVolumeReadOnlyError = 642m NSKeyValueValidationError = 1024, NSFormattingError = 2048, NSUserCancelledError = 3072, NSFileErrorMinimum = 0, NSFileErrorMaximum = 1023, NSValidationErrorMinimum = 1024, NSValidationErrorMaximum = 2047, NSFormattingErrorMinimum = 2048, NSFormattingErrorMaximum = 2559, NSPropertyListReadCorruptError = 3840, NSPropertyListReadUnknownVersionError = 3841, NSPropertyListReadStreamError = 3842, NSPropertyListWriteStreamError = 3851, NSPropertyListErrorMinimum = 3840, NSPropertyListErrorMaximum = 4095 NSExecutableErrorMinimum = 3584, NSExecutableNotLoadableError = 3584, NSExecutableArchitectureMismatchError = 3585, NSExecutableRuntimeMismatchError = 3586, NSExecutableLoadError = 3587, NSExecutableLinkError = 3588, NSExecutableErrorMaximum = 3839, } typedef enum { NSURLErrorUnknown = -1, NSURLErrorCancelled = -999, NSURLErrorBadURL = -1000, NSURLErrorTimedOut = -1001, NSURLErrorUnsupportedURL = -1002, NSURLErrorCannotFindHost = -1003, NSURLErrorCannotConnectToHost = -1004, NSURLErrorDataLengthExceedsMaximum = -1103, 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, NSURLErrorFileDoesNotExist = -1100, NSURLErrorFileIsDirectory = -1101, NSURLErrorNoPermissionsToReadFile = -1102, NSURLErrorSecureConnectionFailed = -1200, NSURLErrorServerCertificateHasBadDate = -1201, NSURLErrorServerCertificateUntrusted = -1202, NSURLErrorServerCertificateHasUnknownRoot = -1203, NSURLErrorServerCertificateNotYetValid = -1204, NSURLErrorClientCertificateRejected = -1205, NSURLErrorClientCertificateRequired = -1206, NSURLErrorCannotLoadFromNetwork = -2000, NSURLErrorCannotCreateFile = -3000, NSURLErrorCannotOpenFile = -3001, NSURLErrorCannotCloseFile = -3002, NSURLErrorCannotWriteToFile = -3003, NSURLErrorCannotRemoveFile = -3004, NSURLErrorCannotMoveFile = -3005, NSURLErrorDownloadDecodingFailedMidStream = -3006, NSURLErrorDownloadDecodingFailedToComplete = -3007 } |
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