swift - The next class has a problem with strong links. Can you show it and resolve this problem? ARC

Question

How can we resolve it with help of weak or unowned?

class Controller {

private var theString = "Hello,"
private var whatToDo: ((String) -> Void)!

init() {
    whatToDo = { str in
        print("(self.theString) (str)")
    }
}

func greetings(_ str: String) {
    whatToDo(str)
}

deinit { print("removed from memory") }

}

question from:https://stackoverflow.com/questions/65890654/the-next-class-has-a-problem-with-strong-links-can-you-show-it-and-resolve-this

Answer 1

Waitting for answers