Learn about @Input() and @Output() in angular

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Create Student class

There are only a few simple attributes (execute the following attributes to quickly generate)
ng generate class entity/student

export class Student {
    id: number;
    name: string;
    age: number;
}

Create child component

ts

import { Component, OnInit, Input, Output, EventEmitter } from '@angular/core';
import { Student } from '../entity/student';
@Component({
  selector: 'app-child',
  templateUrl: './child.component.html',
  styleUrls: ['./child.component.css']
})
export class ChildComponent implements OnInit {
  @Input() stu: Student;
  @Output() deleteEvent = new EventEmitter<number>();
  constructor() { }
  ngOnInit() {
  }
  delete(id) {
    this.stu = null;
    this.deleteEvent.emit(id);
  }
}

html

<p *ngIf="stu">
  {{stu.id}} -- {{stu.name}} -- {{stu.age}}  <button (click)="delete(stu.id)">delete</button>
</p>

Modify app.component

ts

import { Component } from '@angular/core';
import { Student } from './entity/student';
@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css']
})
export class AppComponent {
  stus: Student[] = [
    {id: 1, name: '里斯', age: 3},
    {id: 2, name: '里斯2', age: 4},
    {id: 3, name: '里斯3', age: 5},
  ];
  stu: Student;
  constructor() {
  }
  selected(stu) {
    this.stu = stu;
  }
  deleteStu(id: number) {
    this.stus.forEach((val, index) => {
      if ( val.id === id) {
        this.stus.splice(index, 1);
        return;
      }
    });
  }
}

html

<p>
  <ul>
    <li *ngFor="let stu of stus" (click)="selected(stu)"> {{stu.id}} -- {{stu.name}} -- {{stu.age}} </li>
  </ul>
</p>
<app-child [stu]="stu" (deleteEvent)="deleteStu($event)"></app-child>

@Input() It’s very simple, just give the data of the parent component to a property of the child component;
@Output() The child component creates an EventEmitter, The operation of the child component will trigger the EventEmitter, and then assign this EventEmitter object to a method of the parent component. The modified method will get the parameters given by the EventEmitter object and then process it;

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