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)
}