Understandingpointers.go

package main

import (
	"fmt"
)

type Node struct {
	name string
	age  int
}

type MNode struct {
	name   string
	age    int
	alphas []rune
}

func main() {

	var yo int = 34
	fmt.Printf("actual number - %d with address %p\n", yo, &yo) // actual number - 34 with address 0x14000112018

	fmt.Printf("---------------------------------\n")
	var str string = "Mike"
	fmt.Printf("actual string %s with address %p\n", str, &str) // actual string Mike with address 0x14000104020

	fmt.Printf("---------------------------------\n")
	var arr [2]int
	arr[0] = 1999
	arr[1] = 888
	// array's address = first element of array's address
	fmt.Printf("arr %v with array address %p - \n first element address - %p, \n second element address - %p\n", arr, &arr, &arr[0], &arr[1])
	/*
		output:
		arr [1999 888] with array address 0x14000112030 -
		first element address - 0x14000112030,
		second element address - 0x14000112038
	*/

	fmt.Printf("---------------------------------\n")
	var node Node = Node{name: "Mike Perry", age: 29}
	/*
		- think of struct as an array.
		- address of struct = address of first property of the struct
	*/
	fmt.Printf("Node %v with address %p \n [name: %d name's address: %p], \n [age: %d age's address: %p] \n", node, &node, node.name, &node.name, node.age, &node.age)

	fmt.Printf("---------------------------------\n")
	var nameList []string
	nameList = append(nameList, "Mike")
	nameList = append(nameList, "Perry")
	/*
		- in this case address of nameList is not equal to address of first element of the name list.
		- the reason for that any slice variables stores the pointer to the type.
	*/
	fmt.Printf("slice value: %v slices's address; %p \n [first element: %s, first el address: %p]\n [second element: %s, second el address: %p] \n",
		nameList,
		&nameList,
		nameList[0],
		&nameList[0],
		nameList[1],
		&nameList[1],
	)

	fmt.Printf("---------------------------------\n")

	var nodeList []Node
	nodeList = append(nodeList, Node{name: "Tom1", age: 20})
	nodeList = append(nodeList, Node{name: "Tom2", age: 22})
	fmt.Printf("slice of objects value: %v slices's address; %p \n [first element: %v, first el address: %p]\n [second element: %v, second el address: %p] \n",
		nodeList,
		&nodeList,
		nodeList[0],
		&nodeList[0],
		nodeList[1],
		&nodeList[1],
	)

	fmt.Printf("---------------------------------\n")

	var newNodeList []MNode

	newNodeList = append(newNodeList, MNode{name: "Tom1", age: 20, alphas: []rune("HELLO1")})
	// newNodeList = append(newNodeList, MNode{name: "Tom2", age: 22, alphas: []rune("HELLO1")})
	fmt.Printf("NewNodeList %v, NewNodeListAddress: %p \n NewNodeValue %v, NewNodeValueAddress: %p \n [NewNode name: %s, NewNode name address: %p] \n [NewNode age: %s, NewNode age address: %d], \n [NewNode rune value %v, NewNode rune address --%p]\n [rune valus --> %c %p]\n",
		newNodeList,
		&newNodeList,
		newNodeList[0],
		&(newNodeList[0]), // here...
		newNodeList[0].name,
		&(newNodeList[0].name), // here...
		newNodeList[0].age,
		&(newNodeList[0].age),
		newNodeList[0].alphas,
		&(newNodeList[0].alphas),
		newNodeList[0].alphas[0],
		&(newNodeList[0].alphas[0]),
	)

	fmt.Printf("---------------------------------\n")

	fmt.Printf("newNodeList ptr - %p & newNodeList first el ptr %p\n", &newNodeList, &newNodeList[0])

	fmt.Printf("newNodeList[0] ptr - %p &newNodeList[0].name  %p\n are same", &(newNodeList[0]), &(newNodeList[0].name))

}