Accessing a property in a parent Component

Question

I have a property in a top level Component that is used data from a HTTP source like so (this is in a file called app.ts):

import {UserData} from './services/user-data/UserData';  Component({     selector: 'app', // <app></app>     providers: [...FORM_PROVIDERS],     directives: [...ROUTER_DIRECTIVES],     pipes: [],     template: require('./app.html') }) @RouteConfig([     // stuff here ])  export class App {     // Please note that UserData is an Injectable Service I have written     userStatus: UserStatus;      constructor(private userData: UserData) {         this.userStatus = new UserStatus();     }      ngOnInit() {         this.userData.getUserStatus()             .subscribe(             (status) => {                 this.userStatus = status; // I want to access this in my Child Components...             },             (err) => {console.log(err);},             () => {console.log("User status complete");            }         );     } } 

Now, I have another Component that is a direct child of the top level Component and within it I would like to access the parent's property 'userStatus', here is the child:

Component({     selector: 'profile',     template: require('app/components/profile/profile.html'),     providers: [],     directives: [],     pipes: [] })  export class Profile implements OnInit {     constructor() {      }      ngOnInit() {         // I want to have access with the parent App Component, 'userStatus' propety here... I only want to read this property     } } 

Now in Angular 1.x this would be easy as I could reference $parent in my child controller or (ANTI PATTERN ALERT!!!) I could be so foolish to put this data in my $rootScope.

What would be the best way to access the parent in Angular 2?

Answer 1

There are different way:

• global service

  • see also
  • https://github.com/escardin/angular2-community-faq/blob/master/services.md#how-do-i-communicate-between-components-using-a-shared-service
  • Global Events in Angular 2
  • Plunker

• service shared by parent and injected to the child

  • similar to global service but listed in providers or viewProviders in the parent instead of boostrap(...) and only available to children of parent.

• parent injected to the child and accessed directly by the child

  • disadvantage: tight coupling

export class Profile implements OnInit { constructor(@Host() parent: App) {   parent.userStatus ... } 

• data-binding

export class Profile implements OnInit {   @Input() userStatus:UserStatus;   ... }  <profile [userStatus]="userStatus">