In cocoa message is transmitted by broadcast?

Question

hello,
In cocoa message is transmitted by broadcast,isn't it? Would you know some information about it, please support me some?
Thank you very much!

Answer 1

Are you talking about Objective-C messages or some sort of inter-process communication. From your past posts, I think you are probably looking for inter-process communication information.
One of the problems with MacOS X, is that there are quite a few options to choose from in this area. Apple's Interprocess Communication Overview lists them. That pages lists the options in order of difficulty and performance. The easiest to use and slowest are listed first, the hardest and fasted are last. The two cross-platform options (Pipes and sockets) are listed towards the end.
In Cocoa, Notifications are transmitted by broadcast. Any thread wishing to receive notifications registers interest in them. When those notifications show up, they are handled more-or-less asynchronously.
I say "more-or-less" for a reason. Pretty much all the Cocoa messaging methods, from Distributed Objects to Notifications, have to go through a Run Loop. This will, in effect, serialize those messages for that run loop. So, that isn't quite truly asynchronous.
The only real asynchronous communication methods are hardware interrupts (via IOKit), BSD Signals, and anything else (Mach messaging?) that I don't know about. The only way to get asynchronous communication over a network is to have a normal, serialized network layer that receives the messages and then dumps them, unceremonially, but asychronously, into your application logic, usually via a thread.
The key thing to remember is that Cocoa Distributed Object, Notification Centers, and NSThreads require a solid understanding of how the Run Loop works. I haven't yet had the time to get to that point myself. By the time I get done with it, it is really hacked up and doesn't look as clean as a pthreads/socket implementation. I don't know of any place to get it all explained so that you and I can understand it. Apple's documentation is the best there is and I still don't get it. I think all I need is just more time to play around with it. That is probably what you will have to do as well. Write some test problems for each method and play around with them. That is pretty much your (and my) only option.