pointer.go

// PointerTest project main.go

package main

import (
	"fmt"
)

func main() {

	//http://www.golang-book.com/9
	//We create two person objects and assign them names.

	Bob := Person{"Bob"}
	Frank := Person{"Frank"}

	//Each Person object has a Talk method that accepts a pointer to type Person
	//See below.

	Bob.Talk(&Frank)
	Frank.Talk(&Bob)

	//Bob and Frank talk to each other by using the method and a pointer to the Person they are talking to.
	//Marty is an android.  It has an embedded type Person, with one extra field, Model

	Marty := new(Android)
	Marty.Name = "Marty"
	Marty.Model = "T1000"
	Marty.Talk(&Bob)

	//Marty can talk to Bob using the Talk method, the same way Frank could.

	//Arnold is an android, same as Marty

	Arnold := Android{Person{"Arnold"}, "T1001"}
	//Arnold.Beep(&Marty) //This is an error.
	Marty.Beep(&Arnold)

	/*
	   So, Marty can Beep at Arnold, but Arnold can't beep at Marty!
	   (Maybe one of them is running Windows RT, <snort>)

	   The reason is, Marty was created with the new keyword, which returns a...pointer.
	   That's right! Arnold is a variable of type Android, but
	   Marty is a variable of type pointer to Android.

	   From documentation...
	   This allocates memory for all the fields,
	   sets each of them to their zero value and ***returns a pointer.***

	   Since the Beep method accepts pointers and not structs, we can just pass Marty as is,
	   since it already is a pointer.
	   No need to de-reference with *

	*/

	Arnold.Beep(Marty)

	//If we want to get the value of Marty, we de-ref with the *.

	MartyValue := *Marty

	MartyValue.Talk(&Bob)

}

type Person struct {
	Name string
}

type Android struct {
	Person
	Model string
}

func (p *Person) Talk(TalkingTo *Person) {
	fmt.Printf("%v said, 'Hello there, %v.'\n", p.Name, TalkingTo.Name)
}

func (a *Android) Beep(BeepAt *Android) {
	fmt.Printf("%v beeped, 101010100001 at %v\n", a.Name, BeepAt.Name)
}