26. 消息订阅与发布

消息订阅与发布(pubsub)消息订阅与发布是一种组件间通信的方式，适用于任意组件间通信

使用步骤

1. 安装pubsub： npm i pubsub-js

2. 引入：import pubsub from 'pubsub-js'

3. 接收数据：A组件想接收数据，则在A组件中订阅消息，订阅的回调留在A组件自身

export default {
    methods: {
        demo(msgName, data) {...}
    }
    ...
    mounted() {
			this.pid = pubsub.subscribe('xxx',this.demo)
    }
}

4. 提供数据：pubsub.publish( 'xxx ' ,data)
5. 最好在 beforeDestroy 钩子中，使用pubsub.unsubscribe(pid)取消订阅

School.vue

<template>
	<div class="school">
		<h2>学校名称：{{name}}</h2>
		<h2>学校地址：{{address}}</h2>
	</div>
</template>

<script>
	import pubsub from 'pubsub-js'

	export default {
		name: 'School',
		data() {
			return {
				name:'尚硅谷',
				address:'北京',
			}
		},
		methods: {
			demo(msgName, data) {
				console.log('我是School组件，收到了数据：',msgName, data)
			}
		},
		mounted() {
            // 💖
			this.pubId = pubsub.subscribe('demo', this.demo) // 订阅消息
		},
		beforeDestroy() {
            // 💖
			pubsub.unsubscribe(this.pubId) // 取消订阅
		}
	}
</script>

<style scoped>
	.school{
		background-color: skyblue;
		padding: 5px;
	}
</style>

Student.vue

<template>
  <div class="student">
    <h2>学生姓名：{{name}}</h2>
    <h2>学生性别：{{sex}}</h2>
    <button @click="sendStudentName">把学生名给School组件</button>
  </div>
</template>

<script>
  import pubsub from 'pubsub-js'

  export default {
    name:'Student',
    data() {
      return {
        name:'张三',
        sex:'男',
      }
    },
    methods: {
      sendStudentName(){
        // 💖
        pubsub.publish('demo', this.name) // 发布消息
      }
    }
  }
</script>

<style scoped>
  .student{
    background-color: pink;
    padding: 5px;
    margin-top: 30px;
  }
</style>

Todo-List 之 消息订阅与发布

App.vue

<template>
<div id="root">
  <div class="todo-container">
    <div class="todo-wrap">
      <MyHeader @addTodo="addTodo"/>
      <MyList :todos="todos"/>
      <MyFooter :todos="todos" @checkAllTodo="checkAllTodo" @clearAllTodo="clearAllTodo"/>
  	</div>
  </div>
</div>
</template>

<script>
  import pubsub from 'pubsub-js'	// 习惯第三方库写上面
  import MyHeader from './components/MyHeader.vue'
  import MyList from './components/MyList.vue'
  import MyFooter from './components/MyFooter.vue'


  export default {
    name:'App',
    components: { MyHeader,MyList,MyFooter },
    data() {
      return {
        todos:JSON.parse(localStorage.getItem('todos')) || []
      }
    },
    methods:{
      //添加一个todo
      addTodo(todoObj){
        this.todos.unshift(todoObj)
      },
      //勾选or取消勾选一个todo
      checkTodo(_,id){
        this.todos.forEach((todo)=>{
          if(todo.id === id) todo.done = !todo.done
        })
      },
      //删除一个todo
      deleteTodo(id){
        this.todos = this.todos.filter(todo => todo.id !== id)
      },
      //全选or取消勾选
      checkAllTodo(done){
        this.todos.forEach(todo => todo.done = done)
      },
      //删除已完成的todo
      clearAllTodo(){
        this.todos = this.todos.filter(todo => !todo.done)
      }
    },
    watch:{
      todos:{
        deep:true,
        handler(value){
          localStorage.setItem('todos',JSON.stringify(value))
        }
      }
    },
    mounted(){
      this.pubId = pubsub.subscribe('checkTodo',this.checkTodo)	// 两种对比
      this.$bus.$on('deleteTodo',this.deleteTodo)
    },
    beforeDestroy(){
      pubsub.unsubscribe(this.pubId)
      this.$bus.$off('deleteTodo')
    }
  }
</script>

<style>
  body {
    background: #fff;
  }

  .btn {
    display: inline-block;
    padding: 4px 12px;
    margin-bottom: 0;
    font-size: 14px;
    line-height: 20px;
    text-align: center;
    vertical-align: middle;
    cursor: pointer;
    box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.2), 0 1px 2px rgba(0, 0, 0, 0.05);
    border-radius: 4px;
  }

  .btn-danger {
    color: #fff;
    background-color: #da4f49;
    border: 1px solid #bd362f;
  }

  .btn-danger:hover {
    color: #fff;
    background-color: #bd362f;
  }

  .btn:focus {
    outline: none;
  }

  .todo-container {
    width: 600px;
    margin: 0 auto;
  }
  .todo-container .todo-wrap {
    padding: 10px;
    border: 1px solid #ddd;
    border-radius: 5px;
  }
</style>

MyItem.vue

<template>
    <li>
        <label>
            <input type="checkbox" :checked="todo.done" @click="handleCheck(todo.id)"/>
            <span>{{todo.title}}</span>
        </label>
        <button class="btn btn-danger" @click="handleDelete(todo.id,todo.title)">删除</button>
    </li>
</template>

<script>
    import pubsub from 'pubsub-js'
    export default {
        name:'MyItem',
        props:['todo'],
        methods:{
            handleCheck(id){                    
                pubsub.publish('checkTodo',id)
            },
            handleDelete(id,title){
                if(confirm("确定删除任务："+title+"吗？")){
                    this.$bus.$emit('deleteTodo',id)
                }
            }
        }
    }
</script>

<style scoped>
    li {
        list-style: none;
        height: 36px;
        line-height: 36px;
        padding: 0 5px;
        border-bottom: 1px solid #ddd;
    }

    li label {
        float: left;
        cursor: pointer;
    }

    li label li input {
        vertical-align: middle;
        margin-right: 6px;
        position: relative;
        top: -1px;
    }

    li button {
        float: right;
        display: none;
        margin-top: 3px;
    }

    li:before {
        content: initial;
    }

    li:last-child {
        border-bottom: none;
    }

    li:hover {
        background-color: #eee;
    }

    li:hover button{
        display: block;
    }
</style>