main.go

package main

import "fmt"

type Cat struct{}

func (c Cat) Speak() {
	fmt.Println("meow")
}

type Dog struct{}

func (d Dog) Speak() {
	fmt.Println("woof")
}

type Husky struct {
	Speaker
}

type SpeakerPrefixer struct {
	Speaker
}

func (sp SpeakerPrefixer) Speak() {
	fmt.Print("Prefix: ")
	sp.Speaker.Speak()
}

type Speaker interface {
	Speak()
}

// 'Husky' type doesn't what Speaker type it gets
// as long as it gets some sort of Speaker type
// E.g. You can swap out Dog{} with Cat{}.
func main() {

	h := Husky{SpeakerPrefixer{Dog{}}}
	// Whenever you call h.Speak() it calls
	// the SpeakerPrefixer Speak method, and then
	// that eventually calls sp.Speaker.Speak method.
	// Husky doesn't know or care about it since it just
	// needs some sort of Speak method to call.
	h.Speak()
}

// This is not inheritance, this is 'embedding'

// https://www.youtube.com/watch?v=F4wUrj6pmSI&feature=youtu.be&t=1337

// Call Dispatch
//
// Concrete Types: static               Abstract types: dynamic
// - known at compilcation              - unknown at compilcation
// - very efficient                     - less efficient
// - can't intercept                    - easy to intercept