Decorator Pattern

Decorator structural pattern allows extending the function of an existing object dynamically without altering its internals.

Decorators provide a flexible method to extend functionality of objects.


LogDecorate decorates a function with the signature func(int) int that manipulates integers and adds input/output logging capabilities.

type Object func(int) int

func LogDecorate(fn Object) Object {
    return func(n int) int {
        log.Println("Starting the execution with the integer", n)

        result := fn(n)

        log.Println("Execution is completed with the result", result)

        return result


func Double(n int) int {
    return n * 2

f := LogDecorate(Double)

// Starting execution with the integer 5
// Execution is completed with the result 10

Rules of Thumb

  • Unlike Adapter pattern, the object to be decorated is obtained by injection.
  • Decorators should not alter the interface of an object.