Using unowned for two objects that references each other

RefEachOther

class Unicycle {    
    var wheel: Wheel?
    
    init() {
        self.wheel = Wheel(parent: self)
    }
    
    deinit {
        print ("Unicycle is being deinitialized")
    }
}

class Wheel {
    var parent: Unicycle?
    
    init(parent: Unicycle) {
        self.parent = parent
    }
    
    deinit {
        print ("Wheel is being deinitialized")
    }
}

var cycle: Unicycle? = Unicycle()
cycle = nil