通过chan来实现并发访问控制

通过chan来实现并发访问控制

背景介绍

这是在阅读grom的源码时, 他的schema的初始化方式, 给我留下来很深刻的印象, 本文将通过channel的一些使用来实现实例的并发访问

技术要点

如果chan为空时, 尝试读可以成功, 获得的结果为空

示例代码

package main

import (
  "sync"
  "time"
)

type Demo struct {
  inited chan struct{}
  a      int
}

func (i *Demo) Init() {
  defer close(i.inited)

  i.a = 100
  time.Sleep(time.Second * 2)
}

func (i *Demo) GetInstance() int {
  <-i.inited

  return i.a
}

func main() {
  demo := &Demo{inited: make(chan struct{})}
  waitGroup := sync.WaitGroup{}
  waitGroup.Add(6)
  go func() { defer waitGroup.Done(); demo.Init() }()
  go func() { defer waitGroup.Done(); println(demo.GetInstance()) }()
  go func() { defer waitGroup.Done(); println(demo.GetInstance()) }()
  go func() { defer waitGroup.Done(); println(demo.GetInstance()) }()
  go func() { defer waitGroup.Done(); println(demo.GetInstance()) }()
  go func() { defer waitGroup.Done(); println(demo.GetInstance()) }()
  waitGroup.Wait()
}