最近在写腾讯云IM，发现每次退出登录重新登录，都会报signal SIGABRT崩溃，提示信息如下
Cannot form weak reference to instance (0x10356a040) of class MessageViewController. It is possible that this object was over-released, or is in the process of deallocation.
查了一下发现是过度释放，但在arc里面是很少出现这种情况的。之后就定位问题最后发现在会话类里用到了FBKVOController
- (void)dealloc
{
[self.KVOController unobserveAll];
}
在FBKVOController本类里
- (void)dealloc
{
[self unobserveAll];
}
显然移除监听两次。把会话里的dealloc删除，问题解决。
