观察者模式
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小牛编辑
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2023-12-01
问题
当一个事件发生时你不得不向一些对象发布公告。
解决方案
使用观察者模式(Observer Pattern)。
class PostOffice
constructor: () ->
@subscribers = []
notifyNewItemReleased: (item) ->
subscriber.callback(item) for subscriber in @subscribers when subscriber.item is item
subscribe: (to, onNewItemReleased) ->
@subscribers.push {'item':to, 'callback':onNewItemReleased}
class MagazineSubscriber
onNewMagazine: (item) ->
alert "I've got new "+item
class NewspaperSubscriber
onNewNewspaper: (item) ->
alert "I've got new "+item
postOffice = new PostOffice()
sub1 = new MagazineSubscriber()
sub2 = new NewspaperSubscriber()
postOffice.subscribe "Mens Health", sub1.onNewMagazine
postOffice.subscribe "Times", sub2.onNewNewspaper
postOffice.notifyNewItemReleased "Times"
postOffice.notifyNewItemReleased "Mens Health"
讨论
这里你有一个观察者对象( PostOffice )和可观察对象( MagazineSubscriber, NewspaperSubscriber )。为了通报发布新的周期性可观察对象的事件,应该对 PostOffice 进行订阅。每一个被订阅的对象都存储在 PostOffice 的内部订阅数组中。当新的实体周期发布时每一个订阅者都会收到通知。