Question

I am looking for a high performance inter process communication system in macos X.

What is the best system? AppleEvents or NSNotifications?

Answer 1

Distributed notifications (i.e. notifications sent through NSDistributedNotificationCenter) are most likely not a good option if your goal is high performance and/or reliability. Here is Apple’s own take on this subject:

Posting a distributed notification is an expensive operation. The notification gets sent to a system-wide server that distributes it to all the tasks that have objects registered for distributed notifications. The latency between posting the notification and the notification’s arrival in another task is unbounded. In fact, when too many notifications are posted and the server’s queue fills up, notifications may be dropped. http://developer.apple.com/mac/library/documentation/Cocoa/Reference/Foundation/Classes/NSDistributedNotificationCenter_Class/Reference/Reference.html

Depending on what you mean by “high performance”, you might want to look into distributed objects, or plain old Unix IPC mechanisms (sockets, pipes, shared memory etc).