Go 模式讲解和代码示例

概念示例

get­Instanceget­Instance

协程方面又有什么需要注意的吗？ 每当多个协程想要访问实例时， 单例结构体就必须返回相同的实例。 正因如此， 单例设计模式的实施工作很容易出错。 下方的例子表示了创建单例的正确方式。

一些值得注意的地方：

nilsingle­Instanceget­Instancesingle­Instancesingle­Instancenil

single.go: 单例

package main

import (
	"fmt"
	"sync"
)

var lock = &sync.Mutex{}

type single struct {
}

var singleInstance *single

func getInstance() *single {
	if singleInstance == nil {
		lock.Lock()
		defer lock.Unlock()
		if singleInstance == nil {
			fmt.Println("Creating single instance now.")
			singleInstance = &single{}
		} else {
			fmt.Println("Single instance already created.")
		}
	} else {
		fmt.Println("Single instance already created.")
	}

	return singleInstance
}

main.go: 客户端代码

package main

import (
	"fmt"
)

func main() {

	for i := 0; i < 30; i++ {
		go getInstance()
	}

	// 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()
}

output.txt: 执行结果

Creating single instance now.
Single instance already created.
Single instance already created.
Single instance already created.
Single instance already created.
Single instance already created.
Single instance already created.
Single instance already created.
Single instance already created.
Single instance already created.
Single instance already created.
Single instance already created.
Single instance already created.
Single instance already created.
Single instance already created.
Single instance already created.
Single instance already created.
Single instance already created.
Single instance already created.
Single instance already created.
Single instance already created.
Single instance already created.
Single instance already created.
Single instance already created.
Single instance already created.
Single instance already created.
Single instance already created.
Single instance already created.
Single instance already created.
Single instance already created.