理解父子组件关系：
从父组件看
一，import系列
dashboard component ts
import ScoresComponent 代表dashb是Scores的父组件，
interface ScoreUpdateEvent是父子组件通信的桥梁，下文ts使用 updateStudentScore()方法处理事件
@Component
selector: ‘app-teacher-dashboard’,给此控件命名
imports: [ScoresComponent],导入Scores组件
二html系列
<app-scores
[scores]=”scores”
[loading]=”scoresLoading”
[teacherId]=”teacherId”
(scoreUpdated)=”updateStudentScore($event)”>
app-score是ScoresComponent的子组件，子组件给父传递scores loading teacherId
三ts系列
updateStudentScore(event: ScoreUpdateEvent): void 处理事件
从子组件看
一import
interface ScoreUpdateEvent 父子通信桥梁
selector: ‘app-scores’ 给此组件命名
三ts
@Input（）loading&scores&teacherId 父组件传给子组件，
@Output() scoreUpdated = new EventEmitter
app route ts!URL路径映射到组件！
import { TeacherDashboardComponent } from ‘../teacher/dashboard.component’;
export const routes: Routes = [
// …
{ path: ‘teacher/dashboard’, component: TeacherDashboardComponent },
// …
];