golang 学习之go单例模式

单例模式即只有一个实例，实例的初始化可分为饿汉模式和懒汉模式。

1、饿汉模式

饥(急)不可待，直接实例化。

package singletoninstance

import (
	"fmt"
	"math/rand"
	"time"
)

var singletonInstance *singleton

type singleton struct {
    
    
	random int
}

func init() {
    
    
	rand.Seed(time.Now().UnixNano())
	singletonInstance = &singleton{
    
    random: rand.Int()}
}

func GetSingleton() *singleton {
    
    
	return singletonInstance
}

func (instance *singleton) Printf() {
    
    
	fmt.Printf("value is %v \n", instance)
}

package main

import (
	"designpattern/singleton/singletoninstance"
	"sync"
)

func init() {
    
    
	singletoninstance.GetSingleton().Printf()
}

func main() {
    
    
	var wait sync.WaitGroup
	wait.Add(3)
	for i := 0; i < 3; i++ {
    
    
		go func() {
    
    
			singletoninstance.GetSingleton().Printf()
			wait.Done()
		}()

	}
	wait.Wait()
}

2、懒汉模式

比较懒，不到用时不初始化。

package singletoninstance

import (
	"fmt"
	"math/rand"
	"sync"
	"time"
)

var once sync.Once
var singletonInstance *singleton

type singleton struct {
    
    
	random int
}

func GetSingleton() *singleton {
    
    
	once.Do(func() {
    
    
		rand.Seed(time.Now().UnixNano())
		singletonInstance = &singleton{
    
    random: rand.Int()}
	})
	return singletonInstance
}

func (instance *singleton) Printf() {
    
    
	fmt.Printf("value is %v \n", instance)
}