前言
Crash分为两种，一种是由EXC_BAD_ACCESS引起的，原因是访问了不属于本进程的内存地址，有可能是访问已被释放的内存；另一种是未被捕获的Objective-C异常（NSException），导致程序向自身发送了SIGABRT信号而崩溃
本文主要介绍APP运行时第二种Crash自动防护功能，暂时涵盖容器，字符串，没找到对应的函数，后台返回NSNull导致的崩溃，计时器，kvo，不在主线程中更新UI等崩溃
有空再来慢慢补充其他类型
Demo地址：KJExceptionDemo
设计原理
利用 Objective-C 语言的动态特性，采用AOP面向切面编程的设计思想，交换方法然后拦截处理崩溃信息
| 方法 | 功能 |
| class_getInstanceMethod | 获取实例方法 |
| class_getClassMethod | 获取类方法 |
| method_getImplementation | 获取一个方法的实现 |
| method_setImplementation | 设置一个方法的实现 |
| method_getTypeEncoding | 获取方法实现的编码类型 |
| class_addMethod | 添加方法实现 |
| class_replaceMethod | 用一个方法的实现，替换另一个方法的实现，即aIMP 指向 bIMP，但是bIMP不一定指向aIMP |
| method_exchangeImplementations | 交换两个方法的实现，即 aIMP -> bIMP, bIMP -> aIMP |
交换实例方法
void kExceptionMethodSwizzling(Class clazz, SEL original, SEL swizzled){ Method originalMethod = class_getInstanceMethod(clazz, original); Method swizzledMethod = class_getInstanceMethod(clazz, swizzled); if (class_addMethod(clazz, original, method_getImplementation(swizzledMethod), method_getTypeEncoding(swizzledMethod))) { class_replaceMethod(clazz, swizzled, method_getImplementation(originalMethod), method_getTypeEncoding(originalMethod)); }else{ method_exchangeImplementations(originalMethod, swizzledMethod); } }
交换类方法
void kExceptionClassMethodSwizzling(Class clazz, SEL original, SEL swizzled){ Method originalMethod = class_getClassMethod(clazz, original); Method swizzledMethod = class_getClassMethod(clazz, swizzled); Class metaclass = objc_getMetaClass(NSStringFromClass(clazz).UTF8String); if (class_addMethod(metaclass, original, method_getImplementation(swizzledMethod), method_getTypeEncoding(swizzledMethod))) { class_replaceMethod(metaclass, swizzled, method_getImplementation(originalMethod), method_getTypeEncoding(originalMethod)); }else{ method_exchangeImplementations(originalMethod, swizzledMethod); } }
常见Crash和解决方案
一、没找到对应的函数 - Unrecognized Selector Sent to Instance
| 类型 | 原因 |
| SEL | unrecognized selector sent to instance .h定义但.m没实现 |
| SEL | performSelector: 调用不存在的方法 |
| SEL | delegate 回调前没有判空而是直接调用 |
| SEL | id 类型没有判断类型，强行调用真实类型不存在的方法 |
| SELcopy 修饰的可变的字符串 \ 字典 \ 数组 \ 集合 \ Data，调用可变的方法 | |
消息转发流程图：
解决方案：
交换方法methodSignatureForSelector: 和 forwardInvocation:
对象调用方法经过三个阶段
消息发送：查询cache和方法列表，找到了直接调用，找不到方法会进入下个阶段
动态解析: 调用实例方法resolveInstanceMethod或类方法resolveClassMethod里面可以有一次动态添加方法的机会
消息转发：首先会判断是否有其他对象可以处理方法forwardingTargetForSelector返回一个新的对象，如果没有新的对象进行处理，会调用methodSignatureForSelector方法返回方法签名，然后调用forwardInvocation
选择在消息转发的最后一步来做处理，methodSignatureForSelector:消息获得函数的参数和返回值，然后[self respondsToSelector:aSelector]判断是否有该方法，如果没有返回函数签名，创建一个NSInvocation对象并发送给forwardInvocation
二、容器越界 - 数组和字典
| 类型 | 原因 |
| NSArray | 数组索引越界、插入空对象 |
| NSDictionary | key、value 为空 |
备注：可变的都继承自不可变的，所有可变的分类中，重复的方法就不用再次替换
解决方案：
交换方法，然后防护处理，简单举个例子，NSArray 是一个类簇，它真正的类型是__NSArrayI，交换方法如下
Class __NSArrayI = objc_getClass("__NSArrayI"); /// 越界崩溃方式一：[array objectAtIndex:0]; kExceptionMethodSwizzling(__NSArrayI, @selector(objectAtIndex:), @selector(kj_objectAtIndex:)); /// 越界崩溃方式二：array[0]; kExceptionMethodSwizzling(__NSArrayI, @selector(objectAtIndexedSubscript:), @selector(kj_objectAtIndexedSubscript:));
交换后的处理
- (instancetype)kj_objectAtIndex:(NSUInteger)index{ NSArray *temp = nil; @try { temp = [self kj_objectAtIndex:index]; }@catch (NSException *exception) { NSString *string = @"🍉🍉 crash："; if (self.count == 0) { string = [string stringByAppendingString:@"数组个数为零"]; }else if (self.count <= index) { string = [string stringByAppendingString:@"数组索引越界"]; } [KJCrashManager kj_crashDealWithException:exception CrashTitle:string]; }@finally { return temp; } }
三、KVO
| 类型 | 原因 |
| KVO | 添加了监听，没有移除 |
解决方案：
交换removeObserver:forKeyPath:方法，
- (void)kj_removeObserver:(NSObject*)observer forKeyPath:(NSString *)keyPath{ @try { [self kj_removeObserver:observer forKeyPath:keyPath]; }@catch (NSException *exception) { NSString *string = @"🍉🍉 crash：添加观察者后没有移除观察者导致"; [KJCrashManager kj_crashDealWithException:exception CrashTitle:string]; }@finally { } }
四、NSTimer
| 类型 | 原因 |
| NSTimer | 没有 invalidate，直接销毁 |
| NSTimerNStimer | NStimer 与 target 强引用，内存泄漏 |
解决方案：
交换scheduledTimerWithTimeInterval:target:selector:userInfo:repeats:方法
定义一个抽象类KJProxyProtector，NSTimer实例强引用抽象类，而在抽象类中弱引用target，这样target和NSTimer之间的关系也就是弱引用，意味着target可以自由的释放，从而解决循环引用的问题
五、后台返回NSNull导致的崩溃
| 类型 | 原因 |
| NSNull | 后台返回NSNull导致的崩溃 |
| #### 解决方案： |
交换方法methodSignatureForSelector: 和 forwardInvocation:
六、UIKit Called on Non-Main Thread
解决方案：
交换setNeedsLayout、layoutIfNeeded、layoutSubviews、setNeedsUpdateConstraints方法
[NSThread isMainThread]判断当前线程是否为主线程，如果不是则在主线程执行
异常收集
一、防护类型
目前提供以下七种
typedef NS_OPTIONS(NSInteger, KJCrashProtectorType) { KJCrashProtectorTypeContainer = 1 << 0,// 数组和字典 KJCrashProtectorTypeString = 1 << 1,// 字符串 KJCrashProtectorTypeUnrecognizedSelector = 1 << 2,// 没找到对应的函数 KJCrashProtectorTypeNSNull = 1 << 3,// 后台返回NSNull导致的崩溃 KJCrashProtectorTypeTimer = 1 << 4,// 计时器 KJCrashProtectorTypeKVO = 1 << 5,// kvo KJCrashProtectorTypeUINonMain = 1 << 6,// 不在主线程中刷新UI };
二、开启防护
采用多枚举方式，来快速设置需要开发的防护
/// 开启全部防护 + (void)kj_openAllCrashProtectorManager:(kExceptionBlock)block{ if (block) [KJCrashManager kj_crashBlock:block]; [self kj_openCrashProtectorType: KJCrashProtectorTypeContainer | KJCrashProtectorTypeString | KJCrashProtectorTypeUnrecognizedSelector | KJCrashProtectorTypeNSNull | KJCrashProtectorTypeTimer | KJCrashProtectorTypeKVO]; } /// 开启指定类型防护 + (void)kj_openCrashProtectorType:(KJCrashProtectorType)type{ if (type & KJCrashProtectorTypeContainer) { [NSArray kj_openCrashExchangeMethod]; [NSMutableArray kj_openCrashExchangeMethod]; [NSDictionary kj_openCrashExchangeMethod]; [NSMutableDictionary kj_openCrashExchangeMethod]; } if (type & KJCrashProtectorTypeString) { [NSString kj_openCrashExchangeMethod]; [NSMutableString kj_openCrashExchangeMethod]; [NSAttributedString kj_openCrashExchangeMethod]; [NSMutableAttributedString kj_openCrashExchangeMethod]; } if (type & KJCrashProtectorTypeUnrecognizedSelector) { [NSObject kj_openUnrecognizedSelectorExchangeMethod]; } if (type & KJCrashProtectorTypeNSNull) { [NSNull kj_openNullExchangeMethod]; } if (type & KJCrashProtectorTypeTimer) { [NSTimer kj_openCrashExchangeMethod]; } if (type & KJCrashProtectorTypeKVO) { [NSObject kj_openKVOExchangeMethod]; } if (type & KJCrashProtectorTypeUINonMain) { [UIView kj_openCrashExchangeMethod]; } }
三、解析异常消息
采用正则表达式来匹配出来方法名
/// 解析异常消息 + (NSString*)kj_analysisCallStackSymbols:(NSArray<NSString*>*)callStackSymbols{ __block NSString *msg = nil; NSString *pattern = @"[-\\+]\\[.+\\]";// 匹配出来的格式为 +[类名 方法名] 或者 -[类名 方法名] NSRegularExpression *regularExp = [[NSRegularExpression alloc] initWithPattern:pattern options:NSRegularExpressionCaseInsensitive error:nil]; for (NSInteger i = 2; i < callStackSymbols.count; i++) { NSString *matchesString = callStackSymbols[i]; [regularExp enumerateMatchesInString:matchesString options:NSMatchingReportProgress range:NSMakeRange(0, matchesString.length) usingBlock:^(NSTextCheckingResult * _Nullable result, NSMatchingFlags flags, BOOL * _Nonnull stop) { if (result) { NSString *tempMsg = [matchesString substringWithRange:result.range]; NSString *className = [tempMsg componentsSeparatedByString:@" "].firstObject; className = [className componentsSeparatedByString:@"["].lastObject; if (![className hasSuffix:@")"] && [NSBundle bundleForClass:NSClassFromString(className)] == [NSBundle mainBundle]) { msg = tempMsg; } *stop = YES; } }]; if (msg.length) break; } return msg; }
熟悉又讨厌的崩溃
*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[__NSPlaceholderDictionary initWithObjects:forKeys:count:]: attempt to insert nil object from objects[0]' *** First throw call stack:( 0 CoreFoundation 0x0000000103dca126 __exceptionPreprocess + 242 1 libobjc.A.dylib 0x0000000103c54f78 objc_exception_throw + 48 2 CoreFoundation 0x0000000103e46cdb _CFThrowFormattedException + 194 3 CoreFoundation 0x0000000103e5221e -[__NSPlaceholderDictionary initWithCapacity:].cold.1 + 0 4 CoreFoundation 0x0000000103e351f7 -[__NSPlaceholderDictionary initWithObjects:forKeys:count:] + 227 5 CoreFoundation 0x0000000103dc8da3 +[NSDictionary dictionaryWithObjects:forKeys:count:] + 49 6 KJExtensionHandler 0x00000001033b715f -[ViewController viewDidLoad] + 815 7 UIKitCore 0x000000010d7ac73b -[UIViewController _sendViewDidLoadWithAppearanceProxyObjectTaggingEnabled] + 88 8 UIKitCore 0x000000010d7b1022 -[UIViewController loadViewIfRequired] + 1084 9 UIKitCore 0x000000010d6e800e -[UINavigationController _updateScrollViewFromViewController:toViewController:] + 162 10 UIKitCore 0x000000010d6e82f8 -[UINavigationController _startTransition:fromViewController:toViewController:] + 154 11 UIKitCore 0x000000010d6e9371 -[UINavigationController _startDeferredTransitionIfNeeded:] + 851 12 UIKitCore 0x000000010d6ea6dc -[UINavigationController __viewWillLayoutSubviews] + 150 13 UIKitCore 0x000000010d6caf1e -[UILayoutContainerView layoutSubviews] + 217 14 UIKitCore 0x000000010e43d9ce -[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 2874 15 QuartzCore 0x0000000105546d87 -[CALayer layoutSublayers] + 258 16 QuartzCore 0x000000010554d239 _ZN2CA5Layer16layout_if_neededEPNS_11TransactionE + 575 17 QuartzCore 0x0000000105558f91 _ZN2CA5Layer28layout_and_display_if_neededEPNS_11TransactionE + 65 18 QuartzCore 0x0000000105499078 _ZN2CA7Context18commit_transactionEPNS_11TransactionEdPd + 496 19 QuartzCore 0x00000001054cfe13 _ZN2CA11Transaction6commitEv + 783 20 UIKitCore 0x000000010defe27a __34-[UIApplication _firstCommitBlock]_block_invoke_2 + 81 21 CoreFoundation 0x0000000103d385db __CFRUNLOOP_IS_CALLING_OUT_TO_A_BLOCK__ + 12 22 CoreFoundation 0x0000000103d379ef __CFRunLoopDoBlocks + 434 23 CoreFoundation 0x0000000103d3240c __CFRunLoopRun + 899 24 CoreFoundation 0x0000000103d31b9e CFRunLoopRunSpecific + 567 25 GraphicsServices 0x000000010c7ebdb3 GSEventRunModal + 139 26 UIKitCore 0x000000010dee0af3 -[UIApplication _run] + 912 27 UIKitCore 0x000000010dee5a04 UIApplicationMain + 101 28 KJExtensionHandler 0x00000001033ea92a main + 122 29 libdyld.dylib 0x00000001065eb415 start + 1 30 ??? 0x0000000000000001 0x0 + 1 ) libc++abi.dylib: terminating with uncaught exception of type NSException
防崩处理之后的效果
2020-12-29 15:49:27.649011+0800 KJExceptionDemo[7987:427289] ************ crash 日志 ************ 标题：🍉🍉 crash：ViewController 类出现未找到类方法 异常原因：test_UnrecognizedSelector 🚗🚗类方法未找到🚗🚗 异常地址：-[ViewController testUnrecognizedSelector] 2020-12-29 15:49:27.651701+0800 KJExceptionDemo[7987:427289] ************ crash 日志 ************ 标题：🍉🍉 crash：ViewController 类出现未找到实例方法 异常原因：testCrash:xx: 🚗🚗实例方法未找到🚗🚗 异常地址：-[ViewController testUnrecognizedSelector] 2020-12-29 15:49:27.654808+0800 KJExceptionDemo[7987:427289] ************ crash 日志 ************ 标题：🍉🍉 crash：数组插入数据为空 异常原因：*** -[__NSArrayM insertObject:atIndex:]: object cannot be nil 异常地址：-[ViewController testContainer] 2020-12-29 15:49:27.657423+0800 KJExceptionDemo[7987:427289] ************ crash 日志 ************ 标题：🍉🍉 crash：数组更改索引越界 异常原因：*** -[__NSArrayM setObject:atIndexedSubscript:]: index 4 beyond bounds [0 .. 2] 异常地址：-[ViewController testContainer] 2020-12-29 15:49:27.661423+0800 KJExceptionDemo[7987:427289] ************ crash 日志 ************ 标题：🍉🍉 crash：字符串长度不够 异常原因：*** -[__NSCFConstantString kj_substringFromIndex:]: Index 10 out of bounds; string length 3 异常地址：-[ViewController testString]
Cocoapods安装
pod 'KJExceptionDemo'
