简单的说，每次事件处理时候开始的时候，ios会为我们自动生成一个autorelesepool,，结束的时候释放掉。
之前我们有误解是只有在main程序中有一个autoreleasepool，我们代码中所有autorelease对象都在这个pool中，这个观点是不正确的。
You have to understand the concept of a run-loop. The run loop in iOS waits for some event to happen and then it acts upon it. That event could be the user touching the screen, receiving a call, etc.
For every such event that iOS handles, a new autorelease pool is created at the beginning and drained when the event processing is complete. Theoretically there could be any number of nested autorelease pools created by Cocoa Touch, but the main one you should know about is the event loop.
Maybe this diagram from the Application Life Cycle will help.
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In pseudo-code, this boils down to,
intUIApplicationMain(...){
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while(!shouldQuitApplication){
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Event*someEvent =// wait for next event;
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NSAutoreleasePool*myPool =[[NSAutoreleasePool alloc] init];
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// handle event
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[myPool release];
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}
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}
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These are the event types in iOS
UIEventTypeTouches,
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UIEventTypeMotion,
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UIEventTypeRemoteControl,
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So after every touch, motion, or remote control event is processed, the pool will be drained.
by anerevol