NSUndoManager casting NSUndoManagerProxy crash in Swift code

Question

In our application we\'re using the following code:

let lInvocationTarget = lUndoManager.prepare(withInvocationTarget: self)
let _ = (lInvocationTarget as! M         


        

Answer 1

I found registerUndoWithTarget:handler: is a better API now.

Answer 2

I am so much astonished that I hear your first code works on macOS 10.12. The method prepare(withInvocationTarget:) has been a this-hardly-works-in-Swift thing. Not only the returned proxy object is not the instance of the original class, but neither the object is not a descendent of NSObject (at lease in some former OS Xs).

Anyway, this is one thing worth trying:

let lInvocationTarget = lUndoManager.prepare(withInvocationTarget: self)
_ = (lInvocationTarget as AnyObject).myMethod(self.opacity, undoManager: lUndoManager)