iOS Programming: Nsnotificationcenter Multi-threading situation

In a multithreaded application, notifications are always delivered to the thread in which the notification is posted, whi CH May is the same thread in which a observer registered itself.

In this sentence, notification are both passed and received at post, even if the Add observer is in another thread.

For example: A, b two threads are addobserver. If post in a, the callback is triggered in a and triggered 2 times, regardless of whether the B thread exits at this point.

Source: http://blog.csdn.net/lwl_ls/archive/2011/04/20/6336083.aspx