class SwitchButton {
    let lamp = Lamp()
    var isOn = false
    
    func toggle() {
        isOn = !isOn
        if isOn {
            lamp.lightOn()
        } else {
            lamp.lightOff()
        }
    }
}

class Lamp {
    func lightOn() {
        print("lamp on")
    }
    
    func lightOff() {
        print("lamp off")
    }
}