Go设计模式之观察者模式讲解和代码示例

package main
type Subject interface {
	register(observer Observer)
	deregister(obs Observer)
	notifyAll()
}

package main
import (
	"fmt"
)
type Item struct {
	observerList []Observer // 多个观察者
	name         string
	inStock      bool // 有库存
}
func newItem(name string) *Item {
	return &Item{
		name:    name,
		inStock: false,
	}
}
// 更新状态
func (i *Item) updateAvailability() {
	fmt.Printf("Item %s is now in stock \n", i.name)
	i.inStock = true // 更新状态，有库存 s
	i.notifyAll()
}
func (i *Item) register(o Observer) {
	i.observerList = append(i.observerList, o)
}
func (i *Item) deregister(o Observer) {
	i.observerList = removeFromslice(i.observerList, o)
}
func (i *Item) notifyAll() {
	for _, v := range i.observerList {
		v.update(i.name)
	}
}
func removeFromslice(observerList []Observer, observerToRemove Observer) []Observer {
	observerListLength := len(observerList)
	for i, observer := range observerList {
		if observerToRemove.getID() == observer.getID() {
			observerList[observerListLength-1], observerList[i] = observerList[i], observerList[observerListLength-1]
			return observerList[:observerListLength-1]
		}
	}
	return observerList
}

package main
type Observer interface {
	update(string)
	getID() string
}

package main
import "fmt"
type Customer struct {
	id string
}
func (c *Customer) getID() string {
	return c.id
}
func (c *Customer) update(iteName string) {
	fmt.Printf("Sendint email to customer %s for item %s\n", c.id, iteName)
}

package main
func main() {
	shirtItem := newItem("Nick Shirt")
	observerFirst := &Customer{
		id: "abc@gmail.com",
	}
	observerSecond := &Customer{
		id: "def@gmail.com",
	}
	shirtItem.register(observerFirst)
	shirtItem.register(observerSecond)
	shirtItem.updateAvailability()
}