abstract, interfaces

switch_intrface.cpp

#include <iostream>

class Switchable {
    public:
    virtual void on() = 0;
    virtual void off() = 0;
};

class Switch {
private:
    Switchable& switchable_;
    bool state {false};

public:
    Switch(Switchable& switchable) : switchable_{switchable}
    {}

    void toggle() {
        if (state) {
            state = false;
            switchable_.off();
        } else {
            state = true;
            switchable_.on();
        }
    } 
};

class Lamp : public Switchable
{
    public:
    void on() override {
        std::cout << "Lamp is on\n";
    }

    void off() override {
        std::cout << "Lamp is off\n";
    }
};

int main(int argc, char* argv[])
{
    Lamp my_lamp;
    Switch my_switch(my_lamp);

    my_lamp.on();
    my_lamp.off();

    return 0;
}