iOS中如何防止程序crash

1.程序中常见的crash种类有

  • 1.unSelector 方法未找到
  • 2.KVO未移除，多次添加，多次移除问题
  • 3.数组越界
  • 4.字典赋值key或value为nil
  • 5.NSString substringFromIndex 越界问题
  • 6.NSAttributedString initWithString stirng=nil问题
  • 7.通知deallooc时为移除问题

2.解决方案

1.unSelector可以利用消息转发来解决

消息转发有三种时机

  • 1.在resolveInstanceMethod方法里，添加方法,但是此种方式损害了原有类的结构
+(BOOL)resolveInstanceMethod:(SEL)sel
{
    return YES;
}
  • 2.在下面方法里放回一个自定义对象，同时给此对象添加未实现的方法
-(id)forwardingTargetForSelector:(SEL)aSelector
{
    rerurn obj;
}

3.完整转发，对方法进行签名，自定义对象然后invoke

  • 这里采用第3种方式，生成方法签名，然后forwardInvocation，这里self invoke，因为self没有此方法会捕获到异常，避免程序崩溃
[self safe_exchangeInstanceMethod:[self class] originalSel:@selector(methodSignatureForSelector:) newSel:@selector(safe_methodSignatureForSelector:)];        
[self safe_exchangeInstanceMethod:[self class] originalSel:@selector(forwardInvocation:) newSel:@selector(safe_forwardInvocation:)];

- (NSMethodSignature *)safe_methodSignatureForSelector:(SEL)aSelector
{
    NSMethodSignature *ms = [self safe_methodSignatureForSelector:aSelector];
    if ([self respondsToSelector:aSelector] || ms){
        return ms;
    }
    else{
        return [LSSafeProxy instanceMethodSignatureForSelector:@selector(safe_crashLog)];
    }
}

- (void)safe_forwardInvocation:(NSInvocation *)anInvocation{
    @try {
        [self safe_forwardInvocation:anInvocation];
        
    } @catch (NSException *exception) {
        LSSafeProtectionCrashLog(exception,LSSafeProtectorCrashTypeSelector);
    } @finally {
    }
}
2.KVO未移除，多次添加，多次移除，observeValueForKeyPath:ofObject:change:context:未实现
  • 1.这里交换NSObject以下方法
[self safe_exchangeInstanceMethod:[self class] originalSel:@selector(addObserver:forKeyPath:options:context:) newSel:@selector(safe_addObserver:forKeyPath:options:context:)];
[self safe_exchangeClassMethod:[self class] originalSel:@selector(observeValueForKeyPath:ofObject:change:context:) newSel:@selector(safe_observeValueForKeyPath:ofObject:change:context:)];
[self safe_exchangeInstanceMethod:[self class] originalSel:@selector(removeObserver:forKeyPath:) newSel:@selector(safe_removeObserver:forKeyPath:)];
[self safe_exchangeInstanceMethod:[self class] originalSel:@selector(removeObserver:forKeyPath:context:) newSel:@selector(safe_removeObserver:forKeyPath:context:)];

用safe_downObservedKeyPathArray记录有哪些人监听了自己，用safe_upObservedArray记录自己监听了哪些对象，用来在addObserver时判断是否添加过了，removeObserver时是否已经移除过了，或者压根没有添加过不能移除，在dealloc时自动移除，交换observeValueForKeyPath:ofObject:change:context方法避免监听者未实现此方法

3.数组越界 ，交换数组的一些方法，需要注意的就是数组有类簇，所以需要交换多个类,根据以下规则交换方法即可
// < = iOS 8:下都是__NSArrayI
//iOS9 @[] 是__NSArray0  @[@"fd"]是__NSArrayI
//iOS10以后(含10): 分 __NSArrayI、  __NSArray0、__NSSingleObjectArrayI


//__NSArrayM   NSMutableArray创建的都为__NSArrayM
//__NSArray0   除__NSArrayM 0个元素都为__NSArray0
// __NSSingleObjectArrayI @[@"fds"]只有此形式创建而且仅一个元素为__NSSingleObjectArrayI
//__NSArrayI   @[@"fds",@"fsd"]方式创建多于1个元素 或者 arrayWith创建都是__NSArrayI



//__NSArray0
//arr@[11]   调用的是  [__NSArray0 objectAtIndex:]

//__NSSingleObjectArrayI
//arr@[11] 调用的是  [__NSSingleObjectArrayI objectAtIndex:]

//不可变数组
// <  iOS11： arr@[11]  调用的是[__NSArrayI objectAtIndex:]
// >= iOS11： arr@[11]  调用的是[__NSArrayI objectAtIndexedSubscript]
//  任意系统   [arr objectAtIndex:111]  调用的都是[__NSArrayM objectAtIndex:]

//可变数组
// <  iOS11： arr@[11]  调用的是[__NSArrayM objectAtIndex:]
// >= iOS11： arr@[11]  调用的是[__NSArrayM objectAtIndexedSubscript]
//  任意系统   [arr objectAtIndex:111]  调用的都是[__NSArrayI objectAtIndex:]

[self safe_exchangeInstanceMethod:objc_getClass("__NSPlaceholderArray") originalSel:@selector(initWithObjects:count:) newSel:@selector(safe_initWithObjects:count:)];  
[self safe_exchangeInstanceMethod:objc_getClass("__NSArrayI") originalSel:@selector(objectAtIndex:) newSel:@selector(safe_objectAtIndexI:)];
[self safe_exchangeInstanceMethod:objc_getClass("__NSArrayI") originalSel:@selector(objectAtIndexedSubscript:) newSel:@selector(safe_objectAtIndexedSubscriptI:)];
[self safe_exchangeInstanceMethod:objc_getClass("__NSArray0") originalSel:@selector(objectAtIndex:) newSel:@selector(safe_objectAtIndex0:)];
[self safe_exchangeInstanceMethod:objc_getClass("__NSSingleObjectArrayI") originalSel:@selector(objectAtIndex:) newSel:@selector(safe_objectAtIndexSI:)];

   //方法交换只要一次就好
   Class dClass=NSClassFromString(@"__NSArrayM");
   //由于低于11.0交换此方法会导致有键盘显示的地方，此时退到后台会crash [UIKeyboardLayoutStar release]: message sent to deallocated instance 0x7fd762cc11f0
     if ([UIDevice currentDevice].systemVersion.doubleValue>=11.0) {
          [self safe_exchangeInstanceMethod:dClass originalSel:@selector(objectAtIndex:) newSel:@selector(safe_objectAtIndexM:)];
       }
      //因为11.0以上系统才会调用此方法，所以大于11.0才交换此方法
     if([UIDevice currentDevice].systemVersion.doubleValue>=11.0){
            [self safe_exchangeInstanceMethod:dClass originalSel:@selector(objectAtIndexedSubscript:) newSel:@selector(safe_objectAtIndexedSubscriptM:)];
        }
        
      [self safe_exchangeInstanceMethod:dClass originalSel:@selector(insertObject:atIndex:) newSel:@selector(safe_insertObject:atIndex:)];
      [self safe_exchangeInstanceMethod:dClass originalSel:@selector(removeObjectAtIndex:) newSel:@selector(safe_removeObjectAtIndex:)];
      [self safe_exchangeInstanceMethod:dClass originalSel:@selector(replaceObjectAtIndex:withObject:) newSel:@selector(safe_replaceObjectAtIndex:withObject:)];
4.字典赋值key或value为nil
/*
 大概和NSArray类似  也是iOS8之前都是__NSDictionaryI，其他的参考NSArray
 
 __NSSingleEntryDictionaryI
 @{@"key":@"value"} 此种形式创建而且仅一个可以为__NSSingleEntryDictionaryI
 __NSDictionaryM
 NSMutableDictionary创建都为__NSDictionaryM
 __NSDictionary0
 除__NSDictionaryM外 不管什么方式创建0个key都为__NSDictionary0
 __NSDictionaryI
 @{@"key":@"value",@"key2",@"value2"}此种方式创建多于1个key，或者initWith创建都是__NSDictionaryI

 NSMutableDictionary通过下标方式赋值的时候，value为nil不会崩溃
    iOS11之前会调用 setObject:forKey
    iOS11之后（含11)  setObject:forKeyedSubscript:
 */

 [self safe_exchangeInstanceMethod:NSClassFromString(@"__NSPlaceholderDictionary") originalSel:@selector(initWithObjects:forKeys:count:) newSel:@selector(safe_initWithObjects:forKeys:count:)];
 [self safe_exchangeInstanceMethod:NSClassFromString(@"__NSPlaceholderDictionary") originalSel:@selector(initWithObjects:forKeys:) newSel:@selector(safe_initWithObjects:forKeys:)]; 

   Class dClass=NSClassFromString(@"__NSDictionaryM");
   [self safe_exchangeInstanceMethod:dClass originalSel:@selector(setObject:forKey:) newSel:@selector(safe_setObject:forKey:)];
   [self safe_exchangeInstanceMethod:dClass originalSel:@selector(setObject:forKeyedSubscript:) newSel:@selector(safe_setObject:forKeyedSubscript:)];
   [self safe_exchangeInstanceMethod:dClass originalSel:@selector(removeObjectForKey:) newSel:@selector(safe_removeObjectForKey:)];
5.NSString substringFromIndex 越界问题
        Class dClass=NSClassFromString(@"__NSCFConstantString");
        Class NSPlaceholderStringClass=NSClassFromString(@"NSPlaceholderString");
        
        //initWithString:
        [self safe_exchangeInstanceMethod:NSPlaceholderStringClass originalSel:@selector(initWithString:) newSel:@selector(safe_initWithString:)];
        
        //hasPrefix
        [self safe_exchangeInstanceMethod:dClass originalSel:@selector(hasPrefix:) newSel:@selector(safe_hasPrefix:)];
        
       //hasSuffix
        [self safe_exchangeInstanceMethod:dClass originalSel:@selector(hasSuffix:) newSel:@selector(safe_hasSuffix:)];
        
        //substringFromIndex
        [self safe_exchangeInstanceMethod:dClass originalSel:@selector(substringFromIndex:) newSel:@selector(safe_substringFromIndex:)];
        
        //substringToIndex
        [self safe_exchangeInstanceMethod:dClass originalSel:@selector(substringToIndex:) newSel:@selector(safe_substringToIndex:)];
        
        //substringWithRange
         [self safe_exchangeInstanceMethod:dClass originalSel:@selector(substringWithRange:) newSel:@selector(safe_substringWithRange:)];
        
        //characterAtIndex
         [self safe_exchangeInstanceMethod:dClass originalSel:@selector(characterAtIndex:) newSel:@selector(safe_characterAtIndex:)];
        
         //stringByReplacingOccurrencesOfString:withString:options:range:
        [self safe_exchangeInstanceMethod:dClass originalSel:@selector(stringByReplacingOccurrencesOfString:withString:options:range:) newSel:@selector(safe_stringByReplacingOccurrencesOfString:withString:options:range:)];
        
        //stringByReplacingCharactersInRange:withString:
         [self safe_exchangeInstanceMethod:dClass originalSel:@selector(stringByReplacingCharactersInRange:withString:) newSel:@selector(safe_stringByReplacingCharactersInRange:withString:)];

  
        Class dClass=NSClassFromString(@"__NSCFString");
        Class NSPlaceholderMutableStringClass=NSClassFromString(@"NSPlaceholderMutableString");
        
        //initWithString:
        [self safe_exchangeInstanceMethod:NSPlaceholderMutableStringClass originalSel:@selector(initWithString:) newSel:@selector(safe_initWithString:)];
        
        
        //hasPrefix
        [self safe_exchangeInstanceMethod:dClass originalSel:@selector(hasPrefix:) newSel:@selector(safe_hasPrefix:)];
        
        //hasSuffix
        [self safe_exchangeInstanceMethod:dClass originalSel:@selector(hasSuffix:) newSel:@selector(safe_hasSuffix:)];
        
        
        //substringFromIndex
        [self safe_exchangeInstanceMethod:dClass originalSel:@selector(substringFromIndex:) newSel:@selector(safe_substringFromIndex:)];
        
        //substringToIndex
        [self safe_exchangeInstanceMethod:dClass originalSel:@selector(substringToIndex:) newSel:@selector(safe_substringToIndex:)];
        
        //substringWithRange
        [self safe_exchangeInstanceMethod:dClass originalSel:@selector(substringWithRange:) newSel:@selector(safe_substringWithRange:)];
        
        //characterAtIndex
        [self safe_exchangeInstanceMethod:dClass originalSel:@selector(characterAtIndex:) newSel:@selector(safe_characterAtIndex:)];
        
        
        //stringByReplacingOccurrencesOfString:withString:options:range:
        [self safe_exchangeInstanceMethod:dClass originalSel:@selector(stringByReplacingOccurrencesOfString:withString:options:range:) newSel:@selector(safe_stringByReplacingOccurrencesOfString:withString:options:range:)];
        
        
        //stringByReplacingCharactersInRange:withString:
        [self safe_exchangeInstanceMethod:dClass originalSel:@selector(stringByReplacingCharactersInRange:withString:) newSel:@selector(safe_stringByReplacingCharactersInRange:withString:)];
        
        
        
        //replaceCharactersInRange:withString:
        [self safe_exchangeInstanceMethod:dClass originalSel:@selector(replaceCharactersInRange:withString:) newSel:@selector(safe_replaceCharactersInRange:withString:)];
        
        //replaceOccurrencesOfString:withString:options:range:
        [self safe_exchangeInstanceMethod:dClass originalSel:@selector(replaceOccurrencesOfString:withString:options:range:) newSel:@selector(safe_replaceOccurrencesOfString:withString:options:range:)];
        
        //insertString:atIndex:
        [self safe_exchangeInstanceMethod:dClass originalSel:@selector(insertString:atIndex:) newSel:@selector(safe_insertString:atIndex:)];
        
        //deleteCharactersInRange:
        [self safe_exchangeInstanceMethod:dClass originalSel:@selector(deleteCharactersInRange:) newSel:@selector(safe_deleteCharactersInRange:)];
        
        
        //appendString:
        [self safe_exchangeInstanceMethod:dClass originalSel:@selector(appendString:) newSel:@selector(safe_appendString:)];
        
        
        //setString:
        [self safe_exchangeInstanceMethod:dClass originalSel:@selector(setString:) newSel:@selector(safe_setString:)];
6.NSAttributedString initWithString stirng=nil问题
       Class dClass = NSClassFromString(@"NSConcreteAttributedString");
        
        //initWithString:
        [self safe_exchangeInstanceMethod:dClass originalSel:@selector(initWithString:) newSel:@selector(safe_initWithString:)];
        
        //initWithAttributedString
        [self safe_exchangeInstanceMethod:dClass originalSel:@selector(initWithString:attributes:) newSel:@selector(safe_initWithString:attributes:)];
        
        //initWithString:attributes:
        [self safe_exchangeInstanceMethod:dClass originalSel:@selector(initWithAttributedString:) newSel:@selector(safe_initWithAttributedString:)];

       Class dClass = NSClassFromString(@"NSConcreteMutableAttributedString");
        
        //initWithString:
        [self safe_exchangeInstanceMethod:dClass originalSel:@selector(initWithString:) newSel:@selector(safe_initWithString:)];
        
        //initWithAttributedString
        [self safe_exchangeInstanceMethod:dClass originalSel:@selector(initWithString:attributes:) newSel:@selector(safe_initWithString:attributes:)];
        
        //initWithString:attributes:
        [self safe_exchangeInstanceMethod:dClass originalSel:@selector(initWithAttributedString:) newSel:@selector(safe_initWithAttributedString:)];
        
        
        //以下为NSMutableAttributedString特有方法
        //4.replaceCharactersInRange:withString:
        [self safe_exchangeInstanceMethod:dClass originalSel:@selector(replaceCharactersInRange:withString:) newSel:@selector(safe_replaceCharactersInRange:withString:)];
        
        //5.setAttributes:range:
        [self safe_exchangeInstanceMethod:dClass originalSel:@selector(setAttributes:range:) newSel:@selector(safe_setAttributes:range:)];
        
        
        
        //6.addAttribute:value:range:
        [self safe_exchangeInstanceMethod:dClass originalSel:@selector(addAttribute:value:range:) newSel:@selector(safe_addAttribute:value:range:)];
        
        //7.addAttributes:range:
        [self safe_exchangeInstanceMethod:dClass originalSel:@selector(addAttributes:range:) newSel:@selector(safe_addAttributes:range:)];
        
        //8.removeAttribute:range:
        [self safe_exchangeInstanceMethod:dClass originalSel:@selector(removeAttribute:range:) newSel:@selector(safe_removeAttribute:range:)];
        
        //9.replaceCharactersInRange:withAttributedString:
        [self safe_exchangeInstanceMethod:dClass originalSel:@selector(replaceCharactersInRange:withAttributedString:) newSel:@selector(safe_replaceCharactersInRange:withAttributedString:)];
        
        
        //10.insertAttributedString:atIndex:
        [self safe_exchangeInstanceMethod:dClass originalSel:@selector(insertAttributedString:atIndex:) newSel:@selector(safe_insertAttributedString:atIndex:)];
        
        
        //11.appendAttributedString:
        [self safe_exchangeInstanceMethod:dClass originalSel:@selector(appendAttributedString:) newSel:@selector(safe_appendAttributedString:)];
        
        //12.deleteCharactersInRange:
        [self safe_exchangeInstanceMethod:dClass originalSel:@selector(deleteCharactersInRange:) newSel:@selector(safe_deleteCharactersInRange:)];
        
        //13.setAttributedString:
        [self safe_exchangeInstanceMethod:dClass originalSel:@selector(setAttributedString:) newSel:@selector(safe_setAttributedString:)];
7.通知deallooc时为移除问题

dealloc时不管通知中心添没添加自己，都移除

此框架可以捕获到异常，以及未移除的kvo，打印出信息，回调给用户，用户可以上传到bugly等crash统计平台

//注意线上环境isDebug一定要设置为NO)
[LSSafeProtector openSafeProtectorWithIsDebug:YES block:^(NSException *exception, LSSafeProtectorCrashType crashType) {
//[Bugly reportException:exception];

//此方法相对于上面的方法，好处在于bugly后台查看bug崩溃位置时，不用点击跟踪数据，再点击crash_attach.log，查看里面的额外信息来查看崩溃位置
[Bugly reportExceptionWithCategory:3 name:exception.name reason:[NSString stringWithFormat:@"%@  崩溃位置:%@",exception.reason,exception.userInfo[@"location"]] callStack:@[exception.userInfo[@"callStackSymbols"]] extraInfo:exception.userInfo terminateApp:NO];
}];

具体代码demo请查看github https://github.com/lsmakethebest/LSSafeProtector

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