9.1.1 الگو Singleton

package main

import (
    "fmt"
    "sync"
    "time"
)

type MyLogger struct {
}

var (
    globalLogger *MyLogger
    mu           = &sync.Mutex{}
)

func GetMyLoggerInstance(i int) *MyLogger {
    if globalLogger == nil {
       mu.Lock()
       defer mu.Unlock()
       if globalLogger == nil {
          fmt.Println("creating myLogger instance by", i)
          globalLogger = &MyLogger{}
       }
    } else {
       fmt.Println("myLogger instance already created.")
    }

    return globalLogger
}

func main() {
    for i := 1; i <= 5; i++ {
       go GetMyLoggerInstance(i)
    }
    time.Sleep(time.Second)
}

▶ اجرای کد کپی ✖ بستن خروجی

package main

import (
    "fmt"
    "sync"
    "time"
)

type MyLogger struct {
}

var (
    globalLogger *MyLogger
    once         sync.Once
)

func GetMyLoggerInstance(i int) *MyLogger {
    if globalLogger == nil {
       once.Do(
          func() {
             fmt.Println("creating myLogger instance by", i)
             globalLogger = &MyLogger{}
          })
    } else {
       fmt.Println("myLogger instance already created.")
    }

    return globalLogger
}

func main() {
    for i := 1; i <= 5; i++ {
       go GetMyLoggerInstance(i)
    }
    time.Sleep(time.Second)
}

▶ اجرای کد کپی ✖ بستن خروجی