A brief discussion on several methods of vue3 component communication

<child :msg2="msg2" />
<script setup>
    const props = defineProps({
        // 写法一
        msg2:String
        // 写法二
        msg2:{
            type:String,
            default:&#39;&#39;
        }
    })
    console.log(props) // {msg2:&#39;这是传级子组件的信息2&#39;}
</script>

//Child.vue
<template>
    // 写法一
    <div @click="emit(&#39;myclick&#39;)">按钮</div>
    // 写法二
    <div @click="handleClick">按钮</div>
</template>
<script setup>
    // 方法一
    const emit = defineEmits([&#39;myClick&#39;],[&#39;myClick2&#39;])
    // 方法二
    const handleClick = () => {
        emit(&#39;myClick&#39;,&#39;这是发送给父组件的信息&#39;);
     }
     
     // 方法二 不适用于vue3.2，使用的useContext()已经舍弃
     import { useContext } from &#39;vue&#39;
     const { emit } = useContext()
     const handleClick = () => { 
      emit(&#39;myClick&#39;,&#39;这是发送给父组件的信息&#39;   
     }
</script>

// Parent.vue响应
<template>
    <child @myClick="onMyClick"></child>
</template>
<script setup>
    import child from "./child.vue"
    import onMychilk = (msg) => {
        console.log(msg) // 父组件收到的信息 
    }
</script>

<script setup>
    // 方法一：useContext() vue3.2 之后已经舍弃
    import { useContext } from &#39;vue&#39;
    const ctx = useContext()
    // 对外暴露属性方法等都可以
    ctx.expose({
        childName: &#39;这是子组建的属性&#39;,
        someMethod(){
        console.log(&#39;这是子组件的方法&#39;)
        }
    })
</script>

// Parent.vue 注意 ref="comp"
<template>
    <child ref="comp"></child>
    <button @click="handleClick">按钮</button>
</template>
<script>
    import child from &#39;./child.vue&#39;
    import { ref } from &#39;vue&#39; 
    const comp = ref(null)
    const handleClick = () => {
        console.log(comp.value.childName)
        comp.value.someMethod() // 调用子组件对外暴露的方法
    }
</script>

// 父组件
<child :msg1="msg1" :msg2="msg2" title="3333"></child>
<script setup>
    import child from &#39;./child.vue&#39;
    import { ref,reactive } from &#39;vue
    const msg1 = ref(&#39;111&#39;)
    const msg2 = ref(&#39;222&#39;)
</script>

// 子组件
<script setup>
    import { defineProps,useContext,useAttars } from &#39;vue&#39;
    const props = defineProps({
        msg1: String
    })
    
    // 方法1
    const ctx = useContext()
    console.log(ctx.attars) // {msg2:&#39;222&#39;,title:&#39;333&#39;}
    
    // 方法2 
    const attrs = useAttars()
    console.log(attars)  // {msg2:&#39;2222&#39;,title:&#39;3333&#39;}
</script>

<child v-model:key="key" v-modle:value="value" />
<script>
    import child from &#39;./child.vue&#39;
    import { ref,reactive } from &#39;vue&#39;
    const key = ref(&#39;111&#39;)
    const value = ref(&#39;222&#39;)
</script>

//子组件
<template>
   <button @click="handleClick"></button>
</template>
<script setup>
    // 方法一  v3.2 已被移除
    import { useContext } from &#39;vue&#39;
    const { emit } = useContext()
    
    // 方法二
    import { defineEmits } from &#39;vue&#39;
    const emit = defineEmits([&#39;key&#39;,&#39;value&#39;])
    
    //用法
    const handleClick = () => {
        emit(&#39;update:key&#39;,&#39;新的key&#39;)
        emit(&#39;update:value&#39;,&#39;新的value&#39;)
    }
</script>

    // 父组件
    <script setup>
        import { provide } from &#39;vue&#39;
        const name = provide(&#39;name&#39;)
        console.log(&#39;name&#39;,&#39;沐华&#39;)
    </script>
    //子组件
    <script setup>
        import { inject } from &#39;vue&#39;
        const name = inject(&#39;name&#39;)
        console.log(name) //木华
    </script>

   //store/index.js
   import { createStore } from 'vuex'
   export default createStore({
       state:{count:1},
       getters:{
           getCount:state=>state.count
       },
       mutations:{
           add(state){
               state.count++
           }
       }
      })
    // main.js
    import { createApp } from 'vue'
    import APP from './App.vue'
    import store from './store'
    createApp(APP).use(store).mount("#app")
    
    // 直接使用
    <template>
        <div>
            {{ $store.state.count }}
        </div>
        <button @click="$store.commit(&#39;add&#39;)">
        </button>
    </template>
    
    // 获取
    <script setup>
        import { useStore,computed } from &#39;vuex&#39;
        const store = useStore()
        console.log(store.state.count)
        
        const count = computed (()=>store.state.count)
        console.log(count)
    </script>

mitt.js
import mitt from 'mitt'
const mitt = mitt()
export default mitt

// 组件A 
<script setup>
    import mitt from &#39;./mitt&#39;
    const handleClick = () => {
        mitt.emit(&#39;handleChange&#39;)
    }
</script>
// 组件B 
<script setup>
import mitt from &#39;./mitt&#39;
import { onUnmounted } from &#39;vue&#39;
const someMethod = () => {...}
mitt.on(&#39;handleChange&#39;,someMethod)
onUnmounted(()=>{
    mitt.off(&#39;handleChange&#39;,someMethod)
})
</script>