Observer Design Pattern in GO

The observer pattern is a software design pattern in which an object, called the subject, maintains a list of its dependents, called observers, and notifies them automatically of any state changes, usually by calling one of their methods.

Example

• In the code, I took a simple message posting example over social media (Linkedin, Facebook and Twitter).
• User will input the message by command line and it will observer in all social media portal.

Implementation

• import observer package in our application

• Create Event and Register Observer

• Resiter observer

  privatePortal.Attach(observer) // observer defines Observer object 
  

• Remove observer

  privatePortal.Detach(observer) // observer defines Observer object
  

  • Notify to observer

  privatePortal.Notify(e) // e defines Event object
  

package main

import (
	"bufio"
	ob "design-patterns-in-go/behavioral/observer"
	"fmt"
	"os"
)

func main() {
	fmt.Println("Observer application .......")
	// Initialize notifier
	privatePortal := ob.Initialize()
	fmt.Println("Registering linkedin observer")
	privatePortal.Attach(&ob.Linkedin{})

	fmt.Println("Registering facebook observer")
	privatePortal.Attach(&ob.Facebook{})

	fmt.Println("Registering twitter observer")

	privatePortal.Attach(&ob.Twitter{})

	scanner := bufio.NewScanner(os.Stdin)

	for scanner.Scan() {
		e := ob.Event{Message: scanner.Text()}
		privatePortal.Notify(e)
	}
	fmt.Println(scanner.Err())
}