Summary and examples of vue3 component communication methods

<child :msg2="msg2" />
<script setup>
    const props = defineProps({
        //Writing method 1 msg2:String
        //Writing method 2 msg2:{
            type:String,
            default:''
        }
    })
    console.log(props) // {msg2:'This is the information of the subcomponent 2'}
</script>

//Child.vue
<template>
    //Writing method 1 <div @click="emit('myclick')">button</div>
    //Writing method 2 <div @click="handleClick">button</div>
</template>
<script setup>
    // Method 1 const emit = defineEmits(['myClick'],['myClick2'])
    // Method 2 const handleClick = () => {
        emit('myClick','This is the information sent to the parent component');
     }
      
     // Method 2 is not applicable to vue3.2, the useContext() used has been abandoned import { useContext } from 'vue'
     const { emit } = useContext()
     const handleClick = () => { 
      emit('myClick','This is the information sent to the parent component'   
     }
</script>
 
// Parent.vue responds to <template>
    <child @myClick="onMyClick"></child>
</template>
<script setup>
    import child from "./child.vue"
    import onMychilk = (msg) => {
        console.log(msg) // Information received by the parent component}
</script>

<script setup>
    // Method 1: useContext() has been abandoned since vue3.2 import { useContext } from 'vue'
    const ctx = useContext()
    // Externally exposed properties and methods can be ctx.expose({
        childName: 'This is the property of the child component',
        someMethod(){
        console.log('This is the method of the child component')
        }
    })
</script>
 
// Parent.vue Note ref="comp"
<template>
    <child ref="comp"></child>
    <button @click="handleClick">Button</button>
</template>
<script>
    import child from './child.vue'
    import { ref } from 'vue' 
    const comp = ref(null)
    const handleClick = () => {
        console.log(comp.value.childName)
        comp.value.someMethod() //Call the method exposed by the subcomponent}
</script>

// Parent component <child :msg1="msg1" :msg2="msg2" title="3333"></child>
<script setup>
    import child from './child.vue'
    import { ref,reactive } from 'vue
    const msg1 = ref('111')
    const msg2 = ref('222')
</script>
 
// Subcomponent <script setup>
    import { defineProps,useContext,useAttars } from 'vue'
    const props = defineProps({
        msg1: String
    })
     
    // Method 1
    const ctx = useContext()
    console.log(ctx.attars) // {msg2:'222',title:'333'}
     
    // Method 2 
    const attrs = useAttrs()
    console.log(attars) // {msg2:'2222',title:'3333'}
</script>

<child v-model:key="key" v-modle:value="value" />
<script>
    import child from './child.vue'
    import { ref,reactive } from 'vue'
    const key = ref('111')
    const value = ref('222')
</script>
 
//Subcomponent <template>
   <button @click="handleClick"></button>
</template>
<script setup>
    // Method 1 v3.2 has been removed import { useContext } from 'vue'
    const { emit } = useContext()
     
    // Method 2import { defineEmits } from 'vue'
    const emit = defineEmits(['key','value'])
     
    // Usage const handleClick = () => {
        emit('update:key','new key')
        emit('update:value','new value')
    }
</script>

// Parent component <script setup>
    import { provide } from 'vue'
    const name = provide('name')
    console.log('name','Muhua')
</script>
//Subcomponent <script setup>
    import { inject } from 'vue'
    const name = inject('name')
    console.log(name) //Muhua</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")
  
 // Use <template> directly
     <div>
         {{ $store.state.count }}
     </div>
     <button @click="$store.commit('add')">
     </button>
 </template>
  
 // Get <script setup>
     import { useStore,computed } from 'vuex'
     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

// Component A 
<script setup>
    import mitt from './mitt'
    const handleClick = () => {
        mitt.emit('handleChange')
    }
</script>
// Component B 
<script setup>
import mitt from './mitt'
import { onUnmounted } from 'vue'
const someMethod = () => {...}
mitt.on('handleChange',someMethod)
onUnmounted(()=>{
    mitt.off('handleChange',someMethod)
})
</script>