NSAutoreleasePool。什么时候适合创建新的自动释放池？
在 iOS/CocoaTouch 上，我经常看到在方法中创建 NSAutoreleasePool 新实例的代码。我最近在 NSOperation 中看到了一个。
设置 NSAutoreleasePool 新实例的基本规则是什么？为什么这比简单地依赖于 main.m 中创建的预先存在的发布池更好？
谢谢，
道格
On iOS/CocoaTouch I often see code that creates a new instance of NSAutoreleasePool within a method. I recently saw one within an NSOperation.
What are the ground rules for setting up a new instance of NSAutoreleasePool? Why is this preferable to simply relying on the pre-existing release pool created in main.m?
Thanks,
Doug
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您可以随时使用新的自动释放池，但这并不总是有益的。每当您启动新线程时都需要它，否则该线程中自动释放的对象将被泄漏。在创建和自动释放大量对象的方法中创建新的自动释放池也很常见。例如，如果您有一个循环，在 50 次迭代中每次创建 10 个对象，那么您应该考虑为该方法创建一个自动释放池，如果不是作为循环的一部分，以便为每次迭代创建一个新的对象。
You can use a new autorelease pool whenever you want, but it is not always beneficial. It is required whenever you start a new thread or objects autoreleased in that thread will be leaked. It is also common to create new autorelease pools in a method where you create and autorelease a large number of objects. For example, if you had a loop which created 10 objects in each of 50 iterations, you should consider creating a autorelease pool for that method, if not as part of the loop so that a new one is created for each iteration.
当还没有一个池时（例如在一个新线程中），或者当运行循环中的池不够时（在将运行多次迭代的循环中创建自动释放对象），创建您自己的池，或者当您想要更好地控制您创建的自动释放对象最终何时被释放时。
Create your own pool when there isn't already one in place (such as in a new thread), or when the one in the run loop isn't sufficient (creating autoreleased objects in a loop that will run for many iterations), or when you want increased control over when the autoreleased objects you create are ultimately released.
我在iOS 4.3中进行了测试，执行performSelectorInBackground时需要创建自己的自动释放池。使用 NSOperation 或dispatch_async 时不需要创建。
似乎在iOS >= 5.0中，即使使用performSelectorInBackground，系统也会自动创建自动释放池，所以我找不到需要创建自己的自动释放池的情况。
但无法找到记录的更改。
I tested in iOS 4.3 and you need to create own autorelease pool when execute performSelectorInBackground. You do not need to create when using NSOperation or dispatch_async.
Seems in iOS >= 5.0 the system creates autorelease pool automatically even if use performSelectorInBackground, so I was unable to find a case when you need to create own autorelease pool.
Was unable to find that change documented, though.