golang: Interfaces, type casting

beings.go

package main

import "fmt"

func main() {
	bob := NewHuman("Bob")
	jim := NewHuman("Jim")
	joe := NewHuman("Joe")

	bob.Greet(jim)
	jim.Greet(bob)
	bob.Greet(joe)
	joe.Greet(bob)

	bingo := NewDog("Bingo")
	frank := NewDog("Frank")
	rover := NewDog("Rover")

	bingo.Greet(frank)
	frank.Greet(bingo)
	bingo.Greet(rover)
	rover.Greet(bingo)

	bob.Greet(bingo)
	bingo.Greet(bob)
	jim.Greet(frank)
	frank.Greet(jim)
	joe.Greet(rover)
	rover.Greet(joe)
}

// Being is a being
type Being interface {
	Name() string
	Greet(Being)
}

// HUMAN

// Human is a human being
type Human struct {
	name string
}

// NewHuman returns a new Human
func NewHuman(name string) *Human {
	return &Human{name: name}
}

// SetName sets the Human's name
func (h *Human) SetName(name string) {
	h.name = name
}

// Name is the Human's name
func (h *Human) Name() string {
	return h.name
}

// Greet is the greeting from Human to Being
func (h *Human) Greet(b Being) {
	special := ""
	switch b.(type) {
	case *Human:
		special = " (dude!)"
	case *Dog:
		special = " (arf, arf?)"
	}
	fmt.Printf("Hello %s, I am %s.%s\n", b.Name(), h.Name(), special)
}

// DOG

// Dog is a dog being
type Dog struct {
	name string
}

// NewDog returns a new Dog
func NewDog(name string) *Dog {
	return &Dog{name: name}
}

// SetName sets the Human's name
func (d *Dog) SetName(name string) {
	d.name = name
}

// Name is the Dog's name
func (d *Dog) Name() string {
	return d.name
}

// Greet is the greeting from Dog to Being
func (d *Dog) Greet(b Being) {
	special := ""
	switch b.(type) {
	case *Human:
		special = " (give me a treat)"
	case *Dog:
		special = " (greetings, fellow Dog)"
	}
	fmt.Printf("Woof %s, woof woof %s.%s\n", b.Name(), d.Name(), special)
}