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
- (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
{
// 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 *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
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：
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。
NSLog(@"========%@",[error localizedDescription]);
NSLog(@"========%@",[error localizedFailureReason]);
NSLog(@"========%@",[error localizedRecoverySuggestion]);
二、NSError错误code对照表
Foundation Constants Reference
NSError Codes
NSError codes in the Cocoa error domain.
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,
}
URL Loading System Error Codes
These values are returned as the error code property of an NSError object with the domain “NSURLErrorDomain”.
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
}
三、自定义NSError
系统的NSError是可以自己定制的，以下提供代码来实现并表示如何使用：
YXError.h 与 YXError.m
[objc] view plain copy
//
// YXError.h
// CustomYXError
//
// Copyright (c) 2014年 Y.X. All rights reserved.
//
#import
// 自行添加错误码
typedef enum : NSUInteger {
Crash = -10000,
DisConnect,
Unknow,
} YXErrorCode;
@interface YXError : NSObject
+ (NSError *)errorCode:(YXErrorCode)code userInfo:(NSDictionary *)dic;
+ (NSString *)transformCodeToStringInfo:(YXErrorCode)code;
@end
[objc] view plain copy
//
// YXError.m
// CustomYXError
//
// Copyright (c) 2014年 Y.X. All rights reserved.
//
#import "YXError.h"
static NSDictionary *errorDictionary = nil;
@implementation YXError
+ (void)initialize
{
if (self == [YXError class])
{
errorDictionary = \
@{
/* code : errorWithDomain */
/* ==================================== */
@(Crash) :@"Crash",
@(DisConnect) :@"DisConnect",
@(Unknow) :@"Unknow",
/* ==================================== */
};
}
}
+ (NSError *)errorCode:(YXErrorCode)code userInfo:(NSDictionary *)dic
{
return [NSError errorWithDomain:errorDictionary[@(code)]
code:code
userInfo:dic];
}
+ (NSString *)transformCodeToStringInfo:(YXErrorCode)code
{
return errorDictionary[@(code)];
}
@end
以下是使用的代码：
[objc] view plain copy
//
// AppDelegate.m
// NSError
//
// Copyright (c) 2014年 YouXianMing. All rights reserved.
//
#import "AppDelegate.h"
#import "YXError.h"
@implementation AppDelegate
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
// 定制一个NSError
NSError *error = [YXError errorCode:Crash
userInfo:nil];
NSLog(@"%@", error);
// 翻译一个NSError（将code值翻译成字符串）
NSLog(@"%@", [YXError transformCodeToStringInfo:-10000]);
return YES;
}
@end
