NSUndoManager 是否保留对象？
我执行以下操作：
Path2D *pathToRemove = [path copy];
[[[self undoManager] prepareWithInvocationTarget:self] removePath:pathToRemove atIndex:index];
[pathToRemove autorelease];
我还有一个明确的按钮可以执行以下操作：
[undoManager removeAllActions];
问题是 removeAllActions 使应用程序崩溃。当我删除 [pathToRemove autorelease] 时，它起作用了（或者至少没有崩溃。它仍然可能是内存泄漏）。我想我假设 undoManager 在传递“prepareWithInitationTarget”调用时保留“pathToRemove”。
难道不是这样吗？如果情况并非如此，则可能会发生崩溃，因为对“removeAllActions”的调用正在释放“PathToRemove”对象。但这意味着这是 NSUndoManager 中的一个错误，这种可能性极小。
我可以说我的 copyWithZone 实现也不太可能是罪魁祸首，因为“[pathToRemove description]”和“[path description]”的 NSLog 输出按预期显示不同的地址。
任何帮助将不胜感激。谢谢。
I do the following:
Path2D *pathToRemove = [path copy];
[[[self undoManager] prepareWithInvocationTarget:self] removePath:pathToRemove atIndex:index];
[pathToRemove autorelease];
I also have a clear button that does:
[undoManager removeAllActions];
Problem is that the removeAllActions crashes the app. When I removed the [pathToRemove autorelease], it worked (or at least didn't crash. It could still be a memory leak). I guess I was assuming that the undoManager retained 'pathToRemove' when passed in the 'prepareWithInvocationTarget' call.
Is that not the case? If that is not the case then the crash could happen because the call to 'removeAllActions' is releasing the 'PathToRemove' object. But that would mean it is a bug in NSUndoManager which is highly unlikely.
I can say that my copyWithZone implementation is not likely to be the culprit either since NSLog outputs for '[pathToRemove description]' and '[path description]' show different addresses as expected.
Any help would be appreciated. Thanks.
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根据文档，
prepareWithInitationTarget:方法不保留传递给它的参数。来自NSUndoManager文档，它似乎只是捕获了NSInvocau并稍后重播它。除非特别要求，否则NSInitation对象不会保留其参数中的对象。这并不能完全解释崩溃的原因，因为
removeAllActions只是应该清除撤消堆栈而不对对象执行任何操作。希望这有助于一些人追踪崩溃的根源。
According to the documentation, the
prepareWithInvocationTarget:method doesn't retain the arguments passed to it. From theNSUndoManagerdocumentation, it appears that it simply captures theNSInvocationand later replays it.NSInvocationobjects don't retain the objects in their arguments unless specifically asked to do so.That doesn't quite explain the crash, because
removeAllActionsis just supposed to clear the undo stack and not do anything to the objects.Hope this helps some in tracking down the source of the crash.
根据我的经验，这不是释放/保留问题。您必须在撤消/重做操作后清除堆栈。为此，您可以为 NSUndoManagerDidUndoChangeNotification 通知注册 viewController：
然后清除指定方法上的堆栈：
In my experience, it's not a release/retain issue. You've to clear the stack after the Undo/Redo Operation. To do this you can register your viewController for the NSUndoManagerDidUndoChangeNotification notification:
and then clear the stack onto the specified method: