go memorize

closure.go

// Memorize using closure

package main

import (
	"fmt"
	"time"
)

func urlFunc() func() string {
	var url string

	return func() string {
		if url == "" {
			time.Sleep(3 * time.Second)
			url = "https://masutaka.net"
		}
		return url
	}
}

func main() {
	url := urlFunc()
	fmt.Println("part1")
	fmt.Println(time.Now())
	fmt.Println(url())
	fmt.Println(time.Now())
	fmt.Println(url())
	fmt.Println(time.Now())
	fmt.Println(url())

	fmt.Println()

	url2 := urlFunc()
	fmt.Println("part2")
	fmt.Println(time.Now())
	fmt.Println(url2())
	fmt.Println(time.Now())
	fmt.Println(url2())
	fmt.Println(time.Now())
	fmt.Println(url2())
}

struct.go

// Memorize using struct

package main

import (
	"fmt"
	"time"
)

// Masutaka struct
type Masutaka struct {
	url string
}

func (m *Masutaka) getURL() string {
	if m.url == "" {
		time.Sleep(3 * time.Second)
		m.url = "https://masutaka.net"
	}
	return m.url
}

func main() {
	m := &Masutaka{}
	fmt.Println("part1")
	fmt.Println(time.Now())
	fmt.Println(m.getURL())
	fmt.Println(time.Now())
	fmt.Println(m.getURL())
	fmt.Println(time.Now())
	fmt.Println(m.getURL())

	fmt.Println()

	fmt.Println("part1b")
	fmt.Println(time.Now())
	fmt.Println(m.url)
	fmt.Println(time.Now())
	fmt.Println(m.url)
	fmt.Println(time.Now())
	fmt.Println(m.url)

	fmt.Println()

	m2 := &Masutaka{}
	fmt.Println("part2")
	fmt.Println(time.Now())
	fmt.Println(m2.getURL())
	fmt.Println(time.Now())
	fmt.Println(m2.getURL())
	fmt.Println(time.Now())
	fmt.Println(m2.getURL())
}