class EraseView: UIView {
    ...
    let editViewController = EditImageViewController()
    //array has item
    editViewController.undoEraseButton.enabled = true //here I get the error
    ...
}

var enableUndoButton =  false

class EditImageViewController: UIViewController {

   @IBOutlet weak var undoEraseButton: UIBarButtonItem!

    viewDidLoad() {
        undoEraseButton.enabled = enableUndoButton
    }
}

class EraseView: UIView {
    ...
    //array has item
    enableUndoButton = true //here I get the error
    ...
}