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Decorator

Decorator in Go

Decorator is a structural pattern that allows adding new behaviors to objects dynamically by placing them inside special wrapper objects, called decorators.

Using decorators you can wrap objects countless number of times since both target objects and decorators follow the same interface. The resulting object will get a stacking behavior of all wrappers.

Conceptual Example

pizza.go: Component interface

package main

type IPizza interface {
	getPrice() int
}

veggieMania.go: Concrete component

package main

type VeggeMania struct {
}

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

tomatoTopping.go: Concrete decorator

package main

type TomatoTopping struct {
	pizza IPizza
}

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

cheeseTopping.go: Concrete decorator

package main

type CheeseTopping struct {
	pizza IPizza
}

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

main.go: Client code

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())
}

output.txt: Execution result

Price of veggeMania with tomato and cheese topping is 32

Decorator in Other Languages

Decorator in C# Decorator in C++ Decorator in Java Decorator in PHP Decorator in Python Decorator in Ruby Decorator in Rust Decorator in Swift Decorator in TypeScript