NSError---01

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

//
//  YXError.h
//  CustomYXError
//
//  Copyright (c) 2014年 Y.X. All rights reserved.
//
 
#import <foundation foundation.h="">
 
// 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</foundation>

//

//  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

//

//  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