Go 设计模式

单例模式(Singleton) 

packagemain
import(
"fmt"
"sync"
)
/*
go 单例模式实现方式:
1. 使用 lock,为了并发安全,使用 lock + double check
2. 使用 sync.Once (推荐👍)
3. 使用 init()。The init function is only called once per file in a package, so we can be sure that only a single instance will be created
参考:
- https://blog.cyeam.com/designpattern/2015/08/12/singleton
- https://golangbyexample.com/all-design-patterns-golang/
- https://medium.com/golang-issue/how-singleton-pattern-works-with-golang-2fdd61cd5a7f
*/
varlock=&sync.Mutex{}
typesinglestruct{
}
varsingleInstance*single
funcgetInstance()*single{
ifsingleInstance==nil{// 防止每次调用 getInstance 都频繁加锁
lock.Lock()
deferlock.Unlock()
// double check. 如果超过一个goroutine进入这里,保证只有一个 goroutine 创建
ifsingleInstance==nil{
fmt.Println("Creting Single Instance Now")
singleInstance=&single{}
}else{
fmt.Println("Single Instance already created-1")
}
}else{
fmt.Println("Single Instance already created-2")
}
returnsingleInstance
}
funcmain(){
fori:=0;i<100;i++{
gogetInstance()
}
// Scanln is similar to Scan, but stops scanning at a newline and
// after the final item there must be a newline or EOF.
fmt.Scanln()
}

// 推荐使用 once,实现更加简洁优雅
varoncesync.Once
typesinglestruct{
}
varsingleInstance*single
funcgetInstance()*single{
once.Do(func(){
fmt.Println("Creting Single Instance Now")
singleInstance=&single{}
})
returnsingleInstance
}

参考: