golang decorator pattern code example

Example 1: golang decorator

// this is the type of functions you want to decorate
type StringManipulator func(string) string

// this is your decorator.
func ToLower(m StringManipulator) StringManipulator {
    return func(s string) string {
        lower := strings.ToLower(s)
        return m(lower)
    }
}

Example 2: golang decorator

package main

import (
	"fmt"
)

type pizza interface {
	getPrice() int
}

type veggeMania struct {
}

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

type tomatoTopping struct {
	pizza pizza
}

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

type cheeseTopping struct {
	pizza pizza
}

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

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())
	// Price of veggeMania with tomato and cheese topping is 32
}