package main
 
import "fmt"
 
// class Doorbell
 
type Doorbell struct {
}
 
func (this Doorbell) Ring() {
	fmt.Println("Ring, Ring! Can I come in?")
}
 
// class Telephone
 
type Telephone struct {
}
 
func (this Telephone) Ring() {
	fmt.Println("Ring, Ring! Can we talk?")
}
 
// interfaces are like static duck-typing
 
type Ringer interface {
	Ring()
}
 
// this function takes any object that has a "Ring" method
 
func ringThis(r Ringer) {
	r.Ring()
}
 
// we could even use an anonymous interface
 
func ringThisAnon(r interface { Ring() }) {
	r.Ring()
}
 
func main() {
	// all of this typechecks!
	ringThis(Doorbell{})
	ringThis(Telephone{})
	ringThisAnon(Doorbell{})
	ringThisAnon(Telephone{})
}
 

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