Programming in Objective-C, Sixth Edition

The Event Loop and Memory Allocation

Cocoa and iOS applications run inside what’s called a run or event loop. Think of an event as something that typically occurs by your performing some action (for example, you press a button on the iPhone) or by an implicit action (for example, something arrives over the network). To process the new event, the system creates a new autorelease pool and might call some method in your application to process it. When you’re done handling the event, you return from your method and the system waits for the next event to occur. Before doing so, however, the system drains the autorelease pool. That means that any autoreleased objects you have created in processing that event will be destroyed, unless you have retained ...