objective-c - 为什么执行 "[pool drain]"后，它永远不会返回给调用者？

Question

这是我的代码模板:

int main(int argc, char *argv[]) {
    // create an autorelease pool
    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
    // make sure the application singleton has been instantiated
    NSApplication * application = [NSApplication sharedApplication];
    // instantiate our application delegate
    AppDelegate * applicationDelegate =
                          [[[AppDelegate alloc] init] autorelease];
    // assign our delegate to the NSApplication
    [application setDelegate:applicationDelegate];
    // call the run method of our application
    [application run];
    // drain the autorelease pool
    [pool drain];
    // execution never gets here ..
    return 0;
}

“[池耗尽]”后跟“return 0”为什么永远不会被执行。

但是，我发现了另一个 gnustep 官方示例，它做了同样的事情。

int
main(int argc, char **argv, char** env)
{
  id pool = [NSAutoreleasePool new];
  NSApplication *theApp;

#if LIB_FOUNDATION_LIBRARY
  [NSProcessInfo initializeWithArguments:argv count:argc environment:env];
#endif

  theApp = [NSApplication sharedApplication];
  [theApp setDelegate: [browserController new]];
  [theApp run];

  [pool release];

  return 0;
}

为了证明“[theApp run]”永远不会回来，我已经做了在“[theApp run]”之后立即添加无限循环的练习。但它永远不会被执行。为什么GNUSTEP官方的例子要这样做？

Answer 1

您确定[pool排出]实际上被调用了吗？ [application run] 不会返回，除非调用 [NSApp stop](这种情况很少见)。如果调用更常见的[NSApp终止]，如 the docs say :

Do not bother to put final cleanup code in your application’s main() function—it will never be executed. If cleanup is necessary, perform that cleanup in the delegate’s applicationWillTerminate: method.

一旦您将应用程序移交给运行，您通常就不会再将其取回。