parent-components:

 <div class="item-bottom" v-show="course.showLesson">
    <CourseLesson :lessons="course.name"/>
</div>

...
getCourses(){
            console.log('user=',this.user)
            let studentId = this.user.student.id;
            this.$fetch(`${this.$url}/order/queryByStudentId`,{
                params:{
                    studentId:studentId
                }
            })
            .then(res=>{
                let res_data = res.data;
                console.log('get:/order/queryByStudentId:res_data',res_data);
                if(res_data.success){
                    let orders = res_data.data;
                    orders.forEach(order=>{
                        let orderItem = order.orderItem;
                        let course = orderItem.course;
                        course.noUsedLessonCount = 0;
                        course.usedLessonCount = 0;
                        course.showLesson = false;
                        this.courses.push(course);
...

CourseLesson:

    props:{
        lessons:{
            type:Array,
            default:()=>{
                return []
            }
        }
    },
    watch:{
        lessons(newVal,oldVal){
            alert(1)
            newValue.forEach(lesson=>{
                lesson.showDetail = false;
            })
            console.log('newvalue',newValue)
        }
    },

我在watch里面添加了alert(1),但是根本 就没弹出，可是列表是成功渲染的，这是 为什么？