interfaces_code_snippet_08.go

type monster struct {
	damage int
}

func (m *monster) attack() int {
	return m.damage
}

type attacker interface {
	attack() int
}

type defender interface {
	defend() int
}

func attackOrDefend(attackerDefender interface{}) {
	// Inside this function, we don't know what we're getting, but we can check!
	if attacker, ok := attackerDefender.(attacker); ok {
		fmt.Printf("Attacking with damage %d\n", attacker.attack())
	} else if defender, ok := attackerDefender.(defender); ok {
		fmt.Printf("Defending with damage %d\n", defender.defend())
	}
}

func main() {
	var a attacker = &monster{200}
	attackOrDefend(a) // Prints "Attacking with damage 200"
	attackOrDefend("Hello") // This is allowed, but does nothing.
}