How to print instance address in swift?

Question

I want to print instance address.
But I use protocol to create Person.
And I get error like Generic struct 'Unmanaged' requires that 'Person' be a class type
Have any idea to print parent instance address?

protocol Person {
    var name: String { get }
}

class Parent: Person {
    
    let name: String

    init(name: String) {
        self.name = name
    }
}

let parent = Parent(name: "Jeff")

print(Unmanaged.passUnretained(parent).toOpaque()) //Generic struct 'Unmanaged' requires that 'Person' be a class type