GCD

GCD: grand center dispatch is support for systems with  mutli-core processors.It's really useful when you develop a iOS application or a iOS games. I like this feature!

Ok, let me show you how to use dispatch:

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

// please do something like request net server; download fiel, load big picture 　　

　　[self doSomething];
　　NSLog (@"SecondThread: %@", [NSThread currentThread]);
　　dispatch_async(dispatch_get_main_queue(), ^{


　　　　　　NSLog (@"MainThread: %@", [NSThread currentThread]);

　　　　　　[self callbackMainThread];

　　　　　　//you can refesh the UI

　　});

});

Ok, that's all, isn't it so powerful? i think it is bettwer than you to use create a new NSThread, do something on the new thread , and call peferSelectorOnMainThread:

and you will find dispatch_get_main_queue() will return the mainQueue,and mostly, mainQueue is the UIKit queue.But if you need to dispatch_async to the specified queue

you can use dispatch_get_current_queue and store this queue.

enjoy it!