import { Component, OnInit, Input, OnChanges, SimpleChanges, DoCheck } from '@angular/core';

@Component({

  selector: 'app-child',

  templateUrl: './child.component.html',

  styleUrls: ['./child.component.css']

})

export class ChildComponent implements OnInit, OnChanges, DoCheck {

  @Input()

  greeting: string;

  @Input()

  user: {};

  message = 'hello';

  constructor() { }

  ngOnInit() {

  }

  ngOnChanges(changes: SimpleChanges): void {

    console.log(JSON.stringify(changes, null, ));

  }

  ngDoCheck(): void {

    console.log('子组件Docheck');

  }

}

<div>子组件</div>

<p>问候语{{greeting}}</p>

<p>用户{{user.name}}</p>

<input [(ngModel)]='message'>

import { Component, DoCheck } from '@angular/core';

@Component({

  selector: 'app-root',

  templateUrl: './app.component.html',

  styleUrls: ['./app.component.css']

})

export class AppComponent implements DoCheck {

  greeting = 'nihao';

  user: { name: string } = { name: 'cys' };

  ngDoCheck(): void {

    console.log('父组件Docheck');

  }

}

<input [(ngModel)]="greeting" type="text">

<input [(ngModel)]="user.name" type="text">

<app-child [greeting]="greeting" [user]="user"></app-child>