How to Implement the Decorator Pattern in Go

Core
2026-04-17T12:05:42+00:00
Implement the Decorator Pattern in Go by defining an interface and wrapping concrete components with decorator structs that add behavior.

Implement the Decorator Pattern in Go by defining a common interface, creating a concrete component, and wrapping it with a decorator struct that holds the component and adds behavior.

package main

import "fmt"

type Coffee interface {
    Cost() int
    Description() string
}

type SimpleCoffee struct{}

func (s *SimpleCoffee) Cost() int { return 5 }
func (s *SimpleCoffee) Description() string { return "Simple Coffee" }

type MilkDecorator struct {
    Coffee Coffee
}

func (m *MilkDecorator) Cost() int { return m.Coffee.Cost() + 2 }
func (m *MilkDecorator) Description() string { return m.Coffee.Description() + ", Milk" }

func main() {
    var c Coffee = &SimpleCoffee{}
    c = &MilkDecorator{Coffee: c}
    fmt.Println(c.Description(), c.Cost())
}