如何从vue父组件中获取子组件中的数据

<FormItem label="上传头像" prop="image">
  <uploadImg :width="150" :height="150" :name="'avatar'" size="150px*150px" ref="avatar"></uploadImg></FormItem>
 <FormItem label="上传营业执照" prop="businessLicence">
  <uploadImg :width="350" :height="200" :name="'businessLicence'" size="350px*200px" ref="businessLicence"></uploadImg></FormItem>

/*
    子组件*/<template>
    <input type='file' @change="changeUrl" />
</template>
<script>export default {
    methods: {
        changeUrl(e) {            
        this.$emit('changeUrl', e.currentTarget.files[0].path)
        }
    }
}</script>/*
    父组件*/<template>
    <FormItem label="上传营业执照" prop="businessLicence">
        <uploadImg :width="350" :height="200" :name="'license'" size="350px*200px" @changeUrl="getUrl"></uploadImg>
    </FormItem>
</template>
<script>export default {
    methods: {
        getUrl(path) {            //这个就是你要的path,并且会双向绑定        }
    }
}</script>