import { Component, OnInit, ViewChild } from '@angular/core';@Component({  selector: 'app-child',  templateUrl: './child.component.html',  styleUrls: ['./child.component.css']})export class ChildComponent implements OnInit {  constructor() { }  ngOnInit() {  }  greeting(str: string) {    console.log(str);  }}

  child works!

     
     点我

import { Component, ViewChild } from '@angular/core';import { ChildComponent } from './child/child.component';@Component({  selector: 'app-root',  templateUrl: './app.component.html',  styleUrls: ['./app.component.css']})export class AppComponent {  @ViewChild('child1')  child1: ChildComponent;  constructor() {  }  // tslint:disable-next-line:use-life-cycle-interface  ngOnInit(): void {    this.child1.greeting('child1的问候');  }}