vue组件非常常见的有父子组件通信,兄弟组件通信。而父子组件通信就很简单,父组件会通过 props
向下传数据给子组件,当子组件有事情要告诉父组件时会通过 $emit
事件告诉父组件。今天就来说说如果两个页面没有任何引入和被引入关系,该如何通信了?
如果咱们的应用程序不需要类似Vuex这样的库来处理组件之间的数据通信,就可以考虑Vue中的 事件总线
,即 **EventBus
**来通信。
EventBus的简介
EventBus
又称为事件总线。在Vue中可以使用 EventBus
来作为沟通桥梁的概念,就像是所有组件共用相同的事件中心,可以向该中心注册发送事件或接收事件,所以组件都可以上下平行地通知其他组件,但也就是太方便所以若使用不慎,就会造成难以维护的“灾难”,因此才需要更完善的Vuex作为状态管理中心,将通知的概念上升到共享状态层次。
如何使用EventBus
一、初始化
首先需要创建事件总线并将其导出,以便其它模块可以使用或者监听它。我们可以通过两种方式来处理。先来看第一种,新创建一个 .js 文件,比如 event-bus.js
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// event-bus.js import Vue from 'vue' export const EventBus = new Vue() |
实质上EventBus
是一个不具备 DOM
的组件,它具有的仅仅只是它实例方法而已,因此它非常的轻便。
另外一种方式,可以直接在项目中的 main.js
初始化 EventBus
:
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<span class="token comment">// main.js</span> Vue<span class="token punctuation">.</span>prototype<span class="token punctuation">.</span>$EventBus <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">Vue</span><span class="token punctuation">(</span><span class="token punctuation">)</span> |
EventBus
是一个 全局的事件总线
。稍后再来聊一聊全局的事件总线。
现在我们已经创建了 EventBus
,接下来你需要做到的就是在你的组件中加载它,并且调用同一个方法,就如你在父子组件中互相传递消息一样。
二、发送事件
假设你有两个Vue页面需要通信: A 和 B ,A页面 在按钮上面绑定了点击事件,发送一则消息,想=通知 B页面。
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<span class="token comment"><!-- A.vue --></span> <span class="token tag"><span class="token punctuation"><</span>template<span class="token punctuation">></span></span> <span class="token tag"><span class="token punctuation"><</span>button <span class="token attr-name">@click</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>sendMsg()<span class="token punctuation">"</span></span><span class="token punctuation">></span></span>-<span class="token tag"><span class="token punctuation"></</span>button<span class="token punctuation">></span></span> <span class="token tag"><span class="token punctuation"></</span>template<span class="token punctuation">></span></span> <span class="token tag"><span class="token punctuation"><</span>script<span class="token punctuation">></span></span><span class="token script language-javascript"> <span class="token keyword">import</span> <span class="token punctuation">{</span> EventBus <span class="token punctuation">}</span> <span class="token keyword">from</span> <span class="token string">"../event-bus.js"</span><span class="token punctuation">;</span> <span class="token keyword">export</span> <span class="token keyword">default</span> <span class="token punctuation">{</span> methods<span class="token punctuation">:</span> <span class="token punctuation">{</span> <span class="token function">sendMsg</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> EventBus<span class="token punctuation">.</span><span class="token function">$emit</span><span class="token punctuation">(</span><span class="token string">"aMsg"</span><span class="token punctuation">,</span> <span class="token string">'来自A页面的消息'</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token punctuation">}</span> <span class="token punctuation">}</span> <span class="token punctuation">}</span><span class="token punctuation">;</span> </span><span class="token tag"><span class="token punctuation"></</span>script<span class="token punctuation">></span></span> |
接下来,我们需要在 B页面 中接收这则消息。
三、接收事件
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<span class="token comment"><!-- IncrementCount.vue --></span> <span class="token tag"><span class="token punctuation"><</span>template<span class="token punctuation">></span></span> <span class="token tag"><span class="token punctuation"><</span>p<span class="token punctuation">></span></span>{{msg}}<span class="token tag"><span class="token punctuation"></</span>p<span class="token punctuation">></span></span> <span class="token tag"><span class="token punctuation"></</span>template<span class="token punctuation">></span></span> <span class="token tag"><span class="token punctuation"><</span>script<span class="token punctuation">></span></span><span class="token script language-javascript"> <span class="token keyword">import</span> <span class="token punctuation">{</span> EventBus <span class="token punctuation">}</span> <span class="token keyword">from</span> <span class="token string">"../event-bus.js"</span><span class="token punctuation">;</span> <span class="token keyword">export</span> <span class="token keyword">default</span> <span class="token punctuation">{</span> <span class="token function">data</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">{</span> <span class="token keyword">return</span> <span class="token punctuation">{</span> msg<span class="token punctuation">:</span> <span class="token string">''</span> <span class="token punctuation">}</span> <span class="token punctuation">}</span><span class="token punctuation">,</span> <span class="token function">mounted</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> EventBus<span class="token punctuation">.</span><span class="token function">$on</span><span class="token punctuation">(</span><span class="token string">"aMsg"</span><span class="token punctuation">,</span> <span class="token punctuation">(</span>msg<span class="token punctuation">)</span> <span class="token operator">=></span> <span class="token punctuation">{</span> <span class="token comment">// A发送来的消息</span> <span class="token keyword">this</span><span class="token punctuation">.</span>msg <span class="token operator">=</span> msg<span class="token punctuation">;</span> <span class="token punctuation">}</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token punctuation">}</span> <span class="token punctuation">}</span><span class="token punctuation">;</span> </span><span class="token tag"><span class="token punctuation"></</span>script<span class="token punctuation">></span></span> |
同理我们也可以在 B页面 向 A页面 发送消息。这里主要用到的两个方法:
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<span class="token comment">// 发送消息</span> EventBus<span class="token punctuation">.</span><span class="token function">$emit</span><span class="token punctuation">(</span>channel<span class="token punctuation">:</span> string<span class="token punctuation">,</span> <span class="token function">callback</span><span class="token punctuation">(</span>payload1<span class="token punctuation">,</span>…<span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token comment">// 监听接收消息</span> EventBus<span class="token punctuation">.</span><span class="token function">$on</span><span class="token punctuation">(</span>channel<span class="token punctuation">:</span> string<span class="token punctuation">,</span> <span class="token function">callback</span><span class="token punctuation">(</span>payload1<span class="token punctuation">,</span>…<span class="token punctuation">)</span><span class="token punctuation">)</span> |
前面提到过,如果使用不善,EventBus
会是一种灾难,到底是什么样的“灾难”
了?大家都知道vue是单页应用,如果你在某一个页面刷新了之后,与之相关的EventBus
会被移除,这样就导致业务走不下去。还要就是如果业务有反复操作的页面,EventBus
在监听的时候就会触发很多次,也是一个非常大的隐患。这时候我们就需要好好处理 EventBus
在项目中的关系。通常会用到,在vue页面销毁时,同时移除EventBus
事件监听。
移除事件监听者
如果想移除事件的监听,可以像下面这样操作:
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<span class="token keyword">import</span> <span class="token punctuation">{</span> eventBus <span class="token punctuation">}</span> <span class="token keyword">from</span> <span class="token string">'./event-bus.js'</span> EventBus<span class="token punctuation">.</span><span class="token function">$off</span><span class="token punctuation">(</span><span class="token string">'aMsg'</span><span class="token punctuation">,</span> <span class="token punctuation">{</span><span class="token punctuation">}</span><span class="token punctuation">)</span> |
你也可以使用 EventBus.$off('aMsg')
来移除应用内所有对此某个事件的监听。或者直接调用 EventBus.$off()
来移除所有事件频道,不需要添加任何参数 。
上面就是 EventBus
的使用方法,是不是很简单。上面的示例中我们也看到了,每次使用 EventBus
时都需要在各组件中引入 event-bus.js
。事实上,我们还可以通过别的方式,让事情变得简单一些。那就是创建一个全局的 EventBus
。接下来的示例向大家演示如何在Vue项目中创建一个全局的 EventBus
。
全局EventBus
它的工作原理是发布/订阅方法,通常称为 Pub/Sub
。
创建全局EventBus
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<span class="token keyword">var</span> EventBus <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">Vue</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> Object<span class="token punctuation">.</span><span class="token function">defineProperties</span><span class="token punctuation">(</span>Vue<span class="token punctuation">.</span>prototype<span class="token punctuation">,</span> <span class="token punctuation">{</span> $bus<span class="token punctuation">:</span> <span class="token punctuation">{</span> <span class="token keyword">get</span><span class="token punctuation">:</span> <span class="token keyword">function</span> <span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="token keyword">return</span> EventBus <span class="token punctuation">}</span> <span class="token punctuation">}</span> <span class="token punctuation">}</span><span class="token punctuation">)</span> |
在这个特定的总线中使用两个方法 $on
和 $emit
。一个用于创建发出的事件,它就是 $emit
;另一个用于订阅 $on
:
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<span class="token keyword">var</span> EventBus <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">Vue</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token keyword">this</span><span class="token punctuation">.</span>$bus<span class="token punctuation">.</span><span class="token function">$emit</span><span class="token punctuation">(</span><span class="token string">'nameOfEvent'</span><span class="token punctuation">,</span> <span class="token punctuation">{</span> <span class="token operator">...</span> pass some event data <span class="token operator">...</span><span class="token punctuation">}</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token keyword">this</span><span class="token punctuation">.</span>$bus<span class="token punctuation">.</span><span class="token function">$on</span><span class="token punctuation">(</span><span class="token string">'nameOfEvent'</span><span class="token punctuation">,</span><span class="token punctuation">(</span>$event<span class="token punctuation">)</span> <span class="token operator">=></span> <span class="token punctuation">{</span> <span class="token comment">// ...</span> <span class="token punctuation">}</span><span class="token punctuation">)</span> |
然后我们可以在某个Vue页面使用 this.$bus.$emit("sendMsg", '我是web秀');
,另一个Vue页面使用
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<span class="token keyword">this</span><span class="token punctuation">.</span>$bus<span class="token punctuation">.</span><span class="token function">$on</span><span class="token punctuation">(</span><span class="token string">'updateMessage'</span><span class="token punctuation">,</span> <span class="token keyword">function</span><span class="token punctuation">(</span>value<span class="token punctuation">)</span> <span class="token punctuation">{</span> console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>value<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 我是web秀</span> <span class="token punctuation">}</span><span class="token punctuation">)</span> |
同时也可以使用this.$bus.$off('sendMsg')
来移除事件监听。
总结
本文主要通过简单的实例学习了Vue中有关于 EventBus
相关的知识点。主要涉及了 EventBus
如何实例化,又是如何通过 $emit
发送频道信号,又是如何通过 $on
来接收频道信号。最后简单介绍了如何创建全局的 EventBus
。从实例中我们可以了解到, EventBus
可以较好的实现兄弟组件之间的数据通讯。