Angular2-将数据从路由器出口传输到另一个组件

Question

Am new to Angular2 but I have already made 30+ component and services and used Input, Output, ChangeDetectorRef, Pipes. So pretty much know about Angular2 by now. My app.component.ts looks like this

import { Component } from '@angular/core';
@Component({
    selector: 'soc',
    template: `
        <header-block></header-block>
        <router-outlet></router-outlet>
    `,
})
export class AppComponent { }

As I need my header-block in every page so I added it outside router-block so I don't have to add it everywhere. Now the problem I am having is changing the value of variable in the header-block after doing an action in view inside router-outlet.

For example I have menu which will be visible to the user only after they login.

{{ user_is_logged }}
<ul class="nav navbar-nav navbar-right" *ngIf="user_is_logged == '1'">
    <li><a href="#" (click)="logout($event)">Logout</a></li>
</ul>

user_is_logged is a variable whose value am getting from localStorage in header.block.component.ts

user_is_logged:string = localStorage.getItem("logged");

When the user is not logged in ie user_is_logged is undefined for home.component.ts ( where login logic is written ), I ask the user to login and after successful login am updating the value of user_is_logged variable and also updating the localStorage value of the variable and then triggering detect changes by using the ChangeDetectionRef(cdr) and then routing to user profile

this.user_is_logged = "1";
localStorage.setItem('logged', '1');
this.cdr.detectChanges();
this.router.navigate(['u/'+user_id']); //user_id is from login response from server

The problem is when I reach the user profile after successful login the value of {{ user_is_logged }} never updates even when am using the variable itself or using the value from localStorage or even calling for detection.

Is it possible to do it this way or do I have to add header-block to every page separately? Please ask for more information if I missed something.

---

EDIT ============>

So after going through Subject, BehaviourSubject, AsyncSubject, ReplaySubject, Observables and what not I just couldn't get this to work. This is the last code I have written :

home.page.component.ts (where login happens and has to emit the event)

import { HomeService } from '../services/home.service';
// No observable or subject imported here.

login() {
    // Sending status 1 to HomeService
    this.HomeService.changeStatus("1");
}

home.service.ts (which is imported by both component)

import { BehaviorSubject } from 'rxjs/BehaviorSubject';
// I imported Subject, BehaviourSubject, Observables but cant get it to work

export class HomeService {

    // This looked more reliable than Subject so used this; init with value "0"
    public subjectStream = new BehaviorSubject<string>('0');


    constructor(
    ){
        this.subjectStream.subscribe(value => {
            // Successfully logs value "1" sent by changeStatus below
            console.log(value);
        });
    }


    changeStatus(value: any){

        // Gives value "1" when called by home.page.component.ts
        console.log(value);

        // Looks correct because it successfully sent value to construct
        this.subjectStream.next(value);

    }

}

header.block.component.ts

import { HomeService } from '../services/home.service';
// No observable or subject imported here also.


constructor(
){
    this.HomeService.subjectStream.subscribe(value => {
        // Logs value "0" at beginning but never logs value "1"
        console.log(value);
    });
}

My Log

// logged by constructor when imported by header.block.component
home.service.ts:31                  0

// logged by constructor of header.block.component itself
header.block.component.ts:25        0

// logged by constructor when imported by home.page.component (I think)
home.service.ts:31                  0

// ===================
// Login called here
// ===================

// logged by changeStatus after login after called by home.component
home.service.ts:36                  1 

// logged by constructor after getting event from changeStatus
home.service.ts:31                  1

What am I missing in header.block.component.ts? As the value is successfully updated within the home.service.ts but never goes to header.

Answer 1

Was asked to post this, it is a bare-bones event/subject service to get you started. I use "notifier/notes/note" just so the nomenclature doesn't get confused with "events" and other framework-api mechanisms.

// Constant of named "notes" analogous to named events. 
// I always found it easier to have one event type with a "name",
// rather than creating a specific typed event for every action. 
const Notes = {
    HEADER_BUTTON_CLICKED : 'header_button_clicked'
};

// Any component that wants to send data creates a new "Note" to send.
// Just makes sure you know what all callbacks are getting.
class Note {
    constructor ( name, data ) {
        this.name = name; // Should be from your Notes constant.
        this.data = data; // Can be anything at all.
    }
}

// You inject this service into any component that needs it. 
class NotifierService {

    constructor() {

        let Rx = require ( 'rx' );
        // We'll use Subject here. 
        this.subject = new Rx.Subject ( );
    }

    // You only subscribe if you want to hear notes. 
    subscribe ( callback ) {
        // Subscribing component feeds in a callback.
        // The return of this can be used to unsubscribe as well.
        return this.subject.subscribe ( b => callback ( b ) );
    }

    // Any component with access to this service can just create a note
    // and send it to all subscribers to this service. 
    sendNote ( note ) {
       // Component uses the service to emit a "note" with a 
       // named event and a payload. All subscribers hear it in the
       // callbacks they subscribed with, and can filter on the name
       // in the "note" to make sure it's the event they care about. 
       // This is pretty naive but should give the idea.
       this.subject.onNext ( note );
    }
}
export { NotifierService } // Service to inject
export { Note } // A useful type to send out to subscribers 
export { Notes } // Constant of event/note names.

Typical usage:

import { NotifierService, Notes, Note } from './notifier.service';
... // inject in your constructor either TS or ES6 style...

// I want to hear notes
this.noteSvc.subscribe ( b => this.myCallback ( b ) );

// I want to send a note
this.noteSvc.sendNote ( new Note ( Notes.HEADER_BUTTON_CLICKED, { btnName : 'Home' } );

   // In the callback 
   myCallback ( note ) {
     if ( note.name === Notes.HEADER_BUTTON_CLICKED ) {
        console.log ( note.data ); // whatever the payload is
     }
   }

Answer 2

If you provide HomeService in homepage and header, you get 2 instances of HomeService . If you want to share a service, then provide it only once on the parent component. If you want to share a single instance with your whole application, provide it only at @NgModule() of AppModule