一、NSException简介

1.什么是NSException？

说到NSException你可能不太了解，但是下面的这张图你肯定见过不止一次

exception

这些就是NSException产生的，一旦程序抛出异常，程序就会崩溃，控制台就会有这些崩溃日志。

2、定义一个NSException对象并抛出

NSString*name =@"exception name";

NSString*reason =@"exception reason";

NSException*exception = [NSException exceptionWithName:name reason:reason userInfo:nil];

@throw exception;

运行程序会发现输出和上图类似的日志：

exception

二、异常的简单处理

如果你在开发过程中可能对某段代码不信任，也就是有崩溃的可能，而在线上直接报错又会影响又会体验，那你就可以通过如下的方法处理：

NSMutableArray*array = [NSMutableArray array];

NSString*nilStr =nil;

@try{

//有可能会出现异常的代码，这里写的代码一定会出现问题

[array insertObject:nilStr atIndex:0];

}@catch(NSException *exception) {

//如果@try中的代码出现异常，就会执行这里的代码，也就可以在这里进行相应操作

NSLog(@"exception.name=%@,exception.reason=%@",exception.name,exception.reason);

//如果想要抛出异常就执行如下代码，程序就会崩溃，便于调试

// @throw exception;

}@finally{

//这里的代码一定会执行

}

三、防止潜在的崩溃风险

如果你并不知道程序运行到哪里会出现异常，或者说对于Foundation框架里有非常多常用的方法有导致崩溃的潜在危险，那么该如何拦截潜在的异常风险，并进行相应的处理，防止崩溃的出现呢？

解决办法是：

1.利用iOS的runtime特性和catalog添加新方法，替换掉系统的存在异常风险的方法。

2.利用异常捕获防止程序崩溃，并进行相应处理。

具体的步骤：

1.创建一个HandleCrash类：

TXHandleCrash.h

#import

#define HandleCrashLogBegin @"==========================handleCrashLogBegin==========================="

#define HandleCrashLogEnd @"=============================handleCrash==============================="

#define HandleCrashLogNotification @"HandleCrashLogNotification"

@interfaceTXHandleCrash :NSObject

/**

start handle crash

*/

+(void)startHandle;

/**

exchange class method

*/

+(void)handleClass:(Class)anClass exchangeClassMethod:(SEL)method1 Method:(SEL)method2;

/**

exchange instance method

*/

+(void)handleClass:(Class)anClass exchangeCInstanceMethod:(SEL)method1 Method:(SEL)method2;

/**

handle exception

@param remark remark

*/

+(void)handleException:(NSException*)exception remark:(NSString*)remark;

@end

TXHandleCrash.m

#import"TXHandleCrash.h"

#import

#import"NSDictionary+TXHandleCrash.h"

@implementationTXHandleCrash

+(void)startHandle

{

dispatch_once_ttoken;

dispatch_once(&token , ^{

[NSDictionaryhandleCrash];

});

}

+(void)handleClass:(Class)anClass exchangeClassMethod:(SEL)method1 Method:(SEL)method2

{

Methodmtd1 =class_getClassMethod(anClass, method1);

Methodmtd2 =class_getClassMethod(anClass, method2);

method_exchangeImplementations(mtd1, mtd2);

}

+(void)handleClass:(Class)anClass exchangeCInstanceMethod:(SEL)method1 Method:(SEL)method2

{

Methodmtd1 =class_getInstanceMethod(anClass, method1);

Methodmtd2 =class_getInstanceMethod(anClass, method2);

method_exchangeImplementations(mtd1, mtd2);

}

+(void)handleException:(NSException*)exception remark:(NSString*)remark

{

//堆栈数据

NSArray*callStackSymbols = [NSThreadcallStackSymbols];

//获取在哪个类的哪个方法中实例化的数组，并格式化：-[类名方法名]、+[类名方法名]

NSString*locationMsg = [selflocationExcptionThroughCallStackSymbols:callStackSymbols];

if(!locationMsg) {

locationMsg =@"崩溃位置定位失败，请查看函数调用栈排查错误";

}

NSString*exceptionName = exception.name;

NSString*exceptionReason = exception.reason;

NSString*exceptionLocation = [NSStringstringWithFormat:@"exception location:%@",locationMsg];

NSString*exceptionMsg = [NSStringstringWithFormat:@"\n\n%@\n\n%@\n%@\n%@\n%@\n\n%@\n\n",HandleCrashLogBegin, exceptionName, exceptionReason, exceptionLocation, remark,HandleCrashLogEnd];

NSLog(@"%@", exceptionMsg);

NSDictionary*exceptionInfoDic =@{

@"exceptionName": exceptionName,

@"exceptionReason": exceptionReason,

@"exceptionLocation": exceptionLocation,

@"remark": remark,

@"exception": exception,

@"callStackSymbols": callStackSymbols

};

//将错误信息放在字典里，用通知的形式发送出去

[[NSNotificationCenterdefaultCenter]postNotificationName:HandleCrashLogNotificationobject:niluserInfo:exceptionInfoDic];

}

+(NSString*)locationExcptionThroughCallStackSymbols:(NSArray*)callStackSymbols

{

__blockNSString*locationMsg =nil;

NSLog(@"callStackSymbols=%@",callStackSymbols);

//通过正则匹配出的格式为，-[类名方法名]、+[类名方法名]

NSString*regularExpStr =@"[-\\+]\\[.+\\]";

NSRegularExpression*regularExp = [[NSRegularExpressionalloc]initWithPattern:regularExpStroptions:NSRegularExpressionCaseInsensitiveerror:nil];

for(intindex =2; index

NSString*callStackSymbol = callStackSymbols[index];

[regularExpenumerateMatchesInString:callStackSymboloptions:NSMatchingReportProgressrange:NSMakeRange(0, callStackSymbol.length)usingBlock:^(NSTextCheckingResult*_Nullableresult,NSMatchingFlagsflags,BOOL*_Nonnullstop) {

if(result) {

NSString*tmpLocationMsg = [callStackSymbolsubstringWithRange:result.range];

//get class name

NSString*className = [tmpLocationMsgcomponentsSeparatedByString:@" "].firstObject;

className = [classNamecomponentsSeparatedByString:@"["].lastObject;

NSBundle*bundle = [NSBundlebundleForClass:NSClassFromString(className)];

//filter catalog and system Class

if(![classNamehasPrefix:@")"] && bundle == [NSBundlemainBundle]) {

locationMsg = tmpLocationMsg ;

}

*stop =YES;

}

}];

if(locationMsg.length) {

break;

}

}

returnlocationMsg ;

}

@end

2.创建一个NSDictionary的catalog

NSDictionary+TXHandleCrash.h

#import

@interfaceNSDictionary (TXHandleCrash)

+(void)handleCrash;

@end

NSDictionary+TXHandleCrash.m

#import"NSDictionary+TXHandleCrash.h"

#import"TXHandleCrash.h"

@implementationNSDictionary (TXHandleCrash)

+(void)handleCrash

{

[TXHandleCrashhandleClass:[selfclass]exchangeClassMethod:@selector(dictionaryWithObjects:forKeys:count:)Method:@selector(handleCrashDictionaryWithObjects:forKeys:count:)];

}

+(instancetype)handleCrashDictionaryWithObjects:(constid_Nonnull__unsafe_unretained*)objects forKeys:(constid_Nonnull__unsafe_unretained*)keys count:(NSUInteger)cnt

{

idinstance =nil;

@try{

instance = [selfhandleCrashDictionaryWithObjects:objectsforKeys:keyscount:cnt];

}@catch(NSException *exception) {

[TXHandleCrashhandleException:exceptionremark:@""];

NSUIntegerindex =0;

id_Nonnull__unsafe_unretainednewObjects[cnt];

id_Nonnull__unsafe_unretainednewKeys[cnt];

for(inti =0; i

if(keys[i] && objects[i]) {

newObjects[index] = objects[i];

newKeys[index] = keys[i];

index ++ ;

}

}

instance = [selfhandleCrashDictionaryWithObjects:newObjectsforKeys:newKeyscount:index];

}@finally{

returninstance ;

}

}

@end

3.在Appdelegate中

- (BOOL)application:(UIApplication*)application didFinishLaunchingWithOptions:(NSDictionary*)launchOptions {

[TXHandleCrashstartHandle];

[[NSNotificationCenterdefaultCenter]addObserver:selfselector:@selector(handleException:)name:HandleCrashLogNotificationobject:nil];

returnYES;

}

-(void)handleException:(NSNotification*)notif

{

NSDictionary*exceptionInfo = notif.userInfo;

NSLog(@"----------%@",exceptionInfo);

}

4.在viewcontroller中

- (void)viewDidLoad {

[superviewDidLoad];

NSString*nilStr =nil;

//通过这种方法创建字典其实是调用dictionaryWithObjects:forKeys:count:方法，如果不做任何处理下面的代码就会直接崩溃，现在经常上面那么多的处理就不会崩溃了，并且可以通过AppDelegate中的通知做到收集崩溃日志的目的

NSDictionary*dictionary =@{@"key1":nilStr,@"key2":@"values"};

NSLog(@"dic=%@",dictionary)；

}