Go Example

package main

type cheeseTopping struct {
    pizza pizza
}

func (c *cheeseTopping) getPrice() int {
    pizzaPrice := c.pizza.getPrice()
    return pizzaPrice + 10
}

package main

type pizza interface {
    getPrice() int
}

package main

type tomatoTopping struct {
    pizza pizza
}

func (c *tomatoTopping) getPrice() int {
    pizzaPrice := c.pizza.getPrice()
    return pizzaPrice + 7
}

package main

type veggeMania struct {
}

func (p *veggeMania) getPrice() int {
    return 15
}

package main

import "fmt"

func main() {

    pizza := &veggeMania{}

    //Add cheese topping
    pizzaWithCheese := &cheeseTopping{
        pizza: pizza,
    }

    //Add tomato topping
    pizzaWithCheeseAndTomato := &tomatoTopping{
        pizza: pizzaWithCheese,
    }

    fmt.Printf("Price of veggeMania with tomato and cheese topping is %d\n", pizzaWithCheeseAndTomato.getPrice())
}