Showing the importance of using pointer receivers

pointer-receivers-tick.go

package main

import (
	"fmt"
)

type Item struct {
	TestChan chan int64
}

func (i Item) Tick() {
	i.TestChan <- int64(10)
}

// !!! WARNING THIS FUNCTION WILL NOT WORK !!!
// func (i Item) Subscribe(myChannel chan int64) {
// 	i.TestChan = myChannel
// }

// The issue was a missing *
// The reciever Item should be a pointer reciever
// "Methods with pointer receivers can modify the
// value to which the receiver points"
// https://tour.golang.org/methods/4
func (i *Item) Subscribe(myChannel chan int64) {
	i.TestChan = myChannel
}

func main() {

	tickDataChannel := make(chan int64)

	customItem := Item{
		TestChan: nil,
	}

	// should set the channel on the customItem
	// this will fail to update the value if the
	// reciever isn't a pointer reciever
	customItem.Subscribe(tickDataChannel)

	// run the Tick method to send data down chan
	go customItem.Tick()

	data := <-tickDataChannel

	fmt.Println(data)
}