angular 父组件调用子组件

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);
  }

}

<p>
  child works!
</p>

<app-child #child1></app-child>
<app-child #child2></app-child>
<button (click)="child2.greeting('child2的问候')">点我</button>

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');
  }
}