通过共享服务将数据从父组件发送到子组件

service.ts：

import { Injectable } from '@angular/core';

@Injectable()
export class AppState {
  
  public mylist = [];
  
}

parent.component.ts：

import {Component} from '@angular/core';
import { AppState } from './shared.service';

@Component({
  selector: 'parent-example',
  templateUrl: 'parent.component.html',
})
export class ParentComponent {
  mylistFromParent = [];
  
  constructor(private appState: AppState){
    this.appState.mylist;
  }
  
  add() {
    this.appState.mylist.push({"itemName":"Something"});  
  }
  
}

parent.component.html：

<p> Parent </p>
  <button (click)="add()">Add</button>
<div>
  <child-component></child-component>
</div>

child.component.ts：

import {Component, Input } from '@angular/core';
import { AppState } from './shared.service';

@Component({
  selector: 'child-component',
  template: `
    <h3>Child powered by shared service</h3>
        {{mylist | json}}
  `,
})
export class ChildComponent {
  mylist: any;
  
  constructor(private appState: AppState){
    this.mylist = this.appState.mylist;
  }

}