在setup()钩子函数中调用

父组件

<template>
	<div>
        我是父组件
        <children ref="childrenRef" />
        <button @click="handleChildren">触发子组件</button>
    </div>
</template>

<script lang="ts">
    import { ref, defineComponent } from 'vue'
    import Children from './components/Children.vue';
    export default defineComponent({
    	components: { Children }
        setup() {
            // ref的泛型除了指定any外 还可以指定<InstanceType<typeof Children>>
            const childrenRef = ref<any>();
            const handleChildren = () => childrenRef.value.isChildren();
            return {
                childrenRef,
                handleChildren
            }
        },
    })
</script>

子组件：

<template>
<div>
    我是子组件
</div>
</template>

<script lang="ts">
    import { defineComponent } from 'vue'

    export default defineComponent({
        setup() {
            const isChildren = () => {
                console.log("我是子组件");
            }
            return {
                isChildren,
            }
        }
    })
</script>

如果是在setup()钩子函数中使用，父组件通过ref获取到子组件实例后，直接.value.函数名即可调用子组件所定义的函数。其中ref的泛型可以指定any和InstanceType<typeof Children>

在<srcipt setup>中调用

父组件

<template>
	<div>
        我是父组件
        <children ref="childrenRef" />
        <button @click="handleChildren1">触发子组件1</button>
        <button @click="handleChildren2">触发子组件2</button>
    </div>
</template>

<script setup lang="ts">
    import { ref } from 'vue'
    import Children from './components/Children.vue';
    const childrenRef = ref<InstanceType<typeof Children>>();
    const handleChildren1 = () => childrenRef.value?.isChildren();
    const handleChildren2 = () => childrenRef.value?.isChildren2();
</script>

子组件

<template>
    <div>
        我是子组件
    </div>
</template>

<script setup lang="ts">
    import { defineExpose } from 'vue';
    const isChildren = () => {
        console.log("我是子组件的第一个方法");
    }
    const isChildren2 = () => {
        console.log("我是子组件的第二个方法");
    }
    defineExpose({ isChildren, isChildren2 })
</script>