详解Vue组件之间通信的七种方式

 ```
    // 父组件
    <template>
      <div>
        <h3>props和$emit</h3>
        <Children v-on:changeMsg="changeMsg" :msg="msg"/>
      </div>
    </template>
    <script>
    import Children from './children';
    export default {
      data() {
        return {
          msg: '传递的值'
        }
      },
      components: {
        Children
      },
      methods: {
        changeMsg(val) {
          this.msg = val;
        }
      }
    }
    </script>
    // 子组件
    <template>
      <div>
        <h3 @click="notify">{{msg}}</h3>
      </div>
    </template>
    
    <script>
    export default { 
      data(){
        return {
    
        }
      }, 
      props: ['msg'],
      methods: {
        notify() {
          this.$emit('changeMsg', '修改后的');
        }
      }
    }
    </script>
  ```

```
    // 父组件的代码
    <template>
      <div>
        <h3>{{title}}</h3>
        <button @click="amend">在父组件中修改子组件的标题</button>
        <Children />
      </div>
    </template>
    
    <script>
    import Children from './children.vue';
    export default {
      data() {
        return {
          title: '父组件'
        }
      },
      components: {
        Children
      },
      methods: {
        amend() {
          this.$children[0].title = '修改后的子组件标题';
        }
      }
    }
    </script>
    // 子组件的代码
    <template>
      <div>
        <h3>{{title}}</h3>
        <button @click="amend">在子组件中修改父组件的标题</button>
      </div>
    </template>
    
    <script>
    export default {
      data() {
        return {
          title: '子组件'
        }
      },
      methods: {
        amend() {
          this.$parent.title = '修改后的父组件标题';
        }
      }
    }
    </script>
  ```

 ```
    // 父组件
    <template>
      <div>
        标题:<input type="text" v-model="mymessage"><br />
        <Children v-model="mymessage" />
      </div>
    </template>
    
    <script>
    import Children from './children.vue';
    export default {
      data() {
        return {
          mymessage: '名字',
        }
      },
      components: {
        Children
      }
    }
    </script>
    // 子组件
    <template>
      <div>
        <input type="text" :value="mymessage" @input="changeValue"> 
      </div>
    </template>
    
    <script>
    export default {
      model: {
        prop: 'mymessage',
        event: 'input'
      },
      props: ['mymessage'],
      methods: {
        changeValue(event){
          this.$emit('input', event.target.value);
        }
      }
    }
    </script>
  ```

```
    // 父组件
    <template>
      <div>
        <h3>{{title}}</h3>
        <Children />
      </div>
    </template>
    
    <script>
    import Children from './children.vue';
    export default {
      data() {
        return {
          title: '父组件的标题'
        }
      },
      provide() {
        return {
          updateTitle: this.updateTitle
        }
      },
      methods: {
        updateTitle(title) {
          this.title = title;
        }
      },
      components: {
        Children
      }
    }
    </script>
    // 子组件
    <template>
      <div>
        <button @click="changeAttr">修改父组件的属性</button>
        <Grandson />
      </div>
    </template>
    
    <script>
    import Grandson from './grandson.vue';
    export default {
      data() {
        return {
          
        }
      },
      inject: ['updateTitle'],
      methods: {
        changeAttr() {
          this.updateTitle('子组件修改标题');
        }
      },
      components: {
        Grandson
      }
    }
    </script>
    // 孙组件
    <template>
      <div>
        <button @click="changeAttr">修改祖先组件的属性</button>
      </div>
    </template>
    
    <script>
    export default {
      inject: ['updateTitle'],
      methods: {
        changeAttr() {
          this.updateTitle('孙组件修改标题');
        }
      }
    }
    </script>
  ```

```
  // 父组件
  <template>
    <div>
      <Children :msg="msg" v-on:changeMsg="changeMsg"/>
    </div>
  </template>
  
  <script>
  import Children from './children';
  export default {
    data() {
      return {
        msg: '下发数据',
        test: '123'
      }
    },
    components: {
      Children
    },
    methods: {
      changeMsg() {
        this.msg = '修改后的数据';
      }
    }
  }
  </script>
  // 子组件
  <template>
    <div>
      <Grandson v-bind="$attrs" v-on="$listeners"/>
    </div>
  </template>
  
  <script>
  import Grandson from './grandson';
  export default {
    components: {
      Grandson
    }
  }
  </script>
  // 孙组件
  ```
    <template>
      <div>
        <h3>{{$attrs.msg}}</h3>
        <button @click="change">修改数据</button>
      </div>
    </template>
    
    <script>
    export default {
      data() {
        return {
    
        }
      },
      methods: {
        change() {
          this.$emit('changeMsg')
        }
      }
    }
    </script>

  ```
```

  ```
    // 父组件
    <template>
      <div>
        <One />
        <Two />
      </div>
    </template>
    <script>
    import One from './one.vue';
    import Two from './two.vue';
    export default {
      data() {
        return {
        }
      },
      components: {
        One,
        Two
      }
    }
    </script>
    // one组件
    <template>
      <div>
        <h3>第一个组件</h3>
        <button @click="add">增加数量</button>
      </div>
    </template>
    <script>
    import {BUS} from './index.js';
    export default {
      data() {
        return {
        }
      },
      methods: {
        add() {
          BUS.$emit('add');
        }
      },
      beforeDestory() {
        BUS.$off('add');
      }
    }
    </script>
    // two组件
    <template>
      <div>
        <h3>第二个组件</h3>
        <h3>数量: {{num}}</h3>
      </div>
    </template>
    <script>
    import {BUS} from './index.js';
    export default {
      data() {
        return {
          num: 1
        }
      },
      mounted() {
        BUS.$on('add', () => {
          this.num += 1;
        })
      },
      beforeDestroy() {
        BUS.$off('add');
      }
    }
    </script>
    // index.js 创建的bus
    import Vue from 'vue';
    export const BUS = new Vue({
    }) 
  ```