Registering a redo operation from an async undo with NSUndoManager

问题

With UndoManager.registerUndo(withTarget:selector:object:) I can register an undo operation, and in the provided selector calling this same method again causes the registration of a redo operation. This works fine unless in the selector I'm calling an async function which then needs to register the redo operation, like this:

func job() {  
     doSomething()  
     registerUndo(self, undo)  
}  

func undo() {  
     async {  
          doSomethingElse()  
          registerUndo(self, job)  
     }  
}  

In this case, both calls to registerUndo() actually register an undo operation, and not an undo and then a redo as I would expect. Is there a solution to this problem?

来源：https://stackoverflow.com/questions/58617402/registering-a-redo-operation-from-an-async-undo-with-nsundomanager