A Real-World Example of Go Interfaces

interfacev1.go

package main

// author Dirk Hoekstra 
//link https://medium.com/better-programming/a-real-world-example-of-go-interfaces-98e89b2ddb67


import "fmt"

type User1 struct {
	Name  string
	Email string
}

type UserNotifier1 interface {
	SendMessage(user *User1, message string) error
}

type EmailNotifier1 struct {
}

func (notifier EmailNotifier1) SendMessage(user *User1, message string) error {
	_, err := fmt.Printf("Sending email to %s with content %s\n", user.Name, message)
	return err
}

func main() {
	user := User1{"Dirk", "[email protected]"}
	fmt.Printf("Welcome %s\n", user.Name)

	var userNotifier UserNotifier1
	userNotifier = EmailNotifier1{}
	userNotifier.SendMessage(&user, "Interfaces all the way!")
}

interfacev2.go

package main
// author Dirk Hoekstra 
//link https://medium.com/better-programming/a-real-world-example-of-go-interfaces-98e89b2ddb67

import "fmt"

type User struct {
	Name     string
	Email    string
	Notifier UserNotifier
}

type UserNotifier interface {
	SendMessage(user *User, message string) error
}

type EmailNotifier struct {
}

type SmsNotifier struct {
}

func (notifier SmsNotifier) SendMessage(user *User, message string) error {
	_, err := fmt.Printf("Sending SMS to %s with content %s\n", user.Name, message)
	return err
}

func (notifier EmailNotifier) SendMessage(user *User, message string) error {
	_, err := fmt.Printf("Sending email to %s with content %s\n", user.Name, message)
	return err
}

func (user *User) notify(message string) error {
	return user.Notifier.SendMessage(user, message)
}

func main() {
	user1 := User{"Dirk", "[email protected]", EmailNotifier{}}
	user2 := User{"Justin", "[email protected]", SmsNotifier{}}

	user1.notify("Welcome Email user!")
	user2.notify("Welcome SMS user!")
}