从一个crash理解weak的延迟释放

@interface SSHttpOperation()
...
//网络回调的target
@property(nonatomic, weak)id target;
//外部在发网络请求的时候可以随意设置回调方法, 达到扩展性
@property(nonatomic, assign)SEL didFinishSelector;
...
@end

@implementation SSHttpOperation
- (void)notifyWithResult:(NSDictionary*)result error:(NSError*)error continueWhenCancel:(BOOL)continueWhenCancel {
	//网络请求回来, 进行外部业务回调
    ...
       if(target && [target respondsToSelector:didFinishSelector])  {
           NSMethodSignature *signature = [target methodSignatureForSelector:didFinishSelector];
           NSInvocation *invocation = [NSInvocation invocationWithMethodSignature:signature];
           [invocation setTarget:target]; // 1
           [invocation setSelector:didFinishSelector];
           id wself = self;
           [invocation setArgument:&wself atIndex:2];
           [invocation setArgument:&result atIndex:3];
           [invocation setArgument:&logicError atIndex:4];
           [invocation setArgument:&userInfo atIndex:5];
           [invocation invoke];

       }
      ...
}
@end

Object A

[self.pgcActionManager changePGCAccount:mediaID likeStatus:!hasSubscribed extraTrack:extraTrack likeBlock:^(BOOL isLiked, NSError *error, NSArray<TTVUserAccount *> *recommendUsers) {
       // 一堆业务操作 再block的最后把这个manager置为nil
       ...
       self.pgcActionManager = nil; // 2
   }];

Manager

 
- (void)changePGCAccount:(NSString *)mediaID likeStatus:(BOOL)changeToLike likeBlock:(SSPGCActionManagerLikeBlock)likeBlock{
	...
	self.likeOperation = [SSHttpOperation httpOperationWithURLString:url getParameter:nil postParameter:parameterDict userInfo:userInfo];
    [_likeOperation setQueuePriority:NSOperationQueuePriorityHigh];
    [_likeOperation setFinishTarget:self selector:@selector(operation:finishedResult:error:userInfo:)];
    [SSOperationManager addOperation:_likeOperation];
}

#pragma mark - 网络回调
- (void)operation:(SSHttpOperation*)operation finishedResult:(NSDictionary*)result error:(NSError*)error userInfo:(id)userInfo{
 // 业务逻辑代码 xxx
 //3
 if (_likeBlock) {
	  _likeBlock(isFollow, followError, recommendUsersArray);
   }
 // 后续的业务逻辑代码
 // 4
 [TTVLoginManager showLoginForFollowWithResult:@"你的关注太多,登录保存一下吧" extraTrackDic:@{@"isOver":@(1)} position:self.position];
}

{
  id __weak obj1 = obj;
  NSLog(@"%@", obj1);
}
/* iOS5及之前编译器做法 */
id obj1;
objc_initWeak(&obj1, obj);
id tmp = objc_loadWeakRetained(&obj1);
objc_autorelease(tmp);//错误!!!mistake
NSLog(@"%@", tmp);
objc_destroyWeak(&obj1);

/* 现在的编译器做法*/
id obj = objc_msgSend(NSObject, "new");
id obj1;
objc_initWeak(&obj1, obj);
id tmp = objc_loadWeakRetained(obj1);//objc_loadWeakRetained would increment the reference count to ensure that tmp is alive in the NSLog statement.
NSLog(@"%@", obj1);
objc_release(tmp);
objc_destroyWeak(&obj1);
objc_storeStrong(&obj, 0);//release