Go generator example

main.go

package main

import (
	"fmt"
	"time"
)

type generator struct {
	generateNext chan struct{}
	sendCh       chan int
	i            int
}

func NewGenerator() *generator {
	generateNext := make(chan struct{})
	sendCh := make(chan int)

	go func() {
		i := 0

		for {
			i++ // the generation logic

			if _, ok := <-generateNext; !ok {
				break
			}

			if i == 10 {
				close(sendCh)
				break
			}

			sendCh <- i
		}

		fmt.Println("finished!", i)
	}()

	return &generator{
		generateNext: generateNext,
		sendCh:       sendCh,
	}
}

func (g *generator) Next() bool {
	g.generateNext <- struct{}{}
	i, ok := <-g.sendCh
	g.i = i
	return ok
}

func (g *generator) Scan() int {
	return g.i
}

func (g *generator) Close() {
	close(g.generateNext)
}

func main() {
	g := NewGenerator()
	for g.Next() {
		i := g.Scan()
		fmt.Println(i)
	}

	fmt.Println("now with stop")

	g = NewGenerator()
	for g.Next() {
		i := g.Scan()
		fmt.Println(i)
		if i == 3 {
			g.Close()
			break
		}
	}

	time.Sleep(1)
}