NSAutoreleasePool 自动释放池是如何工作的? [英] How does the NSAutoreleasePool autorelease pool work?

问题描述

据我所知，使用alloc、新或副本创建的任何内容都需要手动释放.例如:

As I understand it, anything created with an alloc, new, or copy needs to be manually released. For example:

int main(void) {
    NSString *string;
    string = [[NSString alloc] init];
    /* use the string */
    [string release];
}

不过，我的问题是这不是同样有效吗?:

My question, though, is wouldn't this be just as valid?:

int main(void) {
    NSAutoreleasePool *pool;
    pool = [[NSAutoreleasePool alloc] init];
    NSString *string;
    string = [[[NSString alloc] init] autorelease];
    /* use the string */
    [pool drain];
}

推荐答案

是的，您的第二个代码片段完全有效.

Yes, your second code snippit is perfectly valid.

每次将 -autorelease 发送到对象时，都会将其添加到最内部的自动释放池中.当池被排空时，它只是向池中的所有对象发送 -release.

Every time -autorelease is sent to an object, it is added to the inner-most autorelease pool. When the pool is drained, it simply sends -release to all the objects in the pool.

自动释放池只是一种便利，它允许您将发送 -release 推迟到稍后".稍后"可能发生在多个地方，但在 Cocoa GUI 应用程序中最常见的是在当前运行循环周期结束时.

Autorelease pools are simply a convenience that allows you to defer sending -release until "later". That "later" can happen in several places, but the most common in Cocoa GUI apps is at the end of the current run loop cycle.

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