Comunication via a service

import { Component,Input } from '@angular/core';
import { AppService } from './app.service';

@Component({
  moduleId: module.id,
  selector: 'my-app',
  template: `
    <app-parent></app-parent>
    
    <app-child></app-child>
  `,
  providers: [AppService]
  
})
export class AppComponent {
}

@Component({
  selector: 'app-child',
  template: `
    <h3>Child say</h3>
    <button (click)="say()" >Say</button>
    Daddy say: {{daddyMess}}
  `
})
export class AppChildComponent {

  daddyMess = '';
  constructor(private _appService: AppService) {

    // Lắng nghe câu trả lời từ ông già
    _appService.parentSaid$.subscribe(mess => {
      this.daddyMess = mess;
    });
  }

  say() {
    this._appService.childSay('daddy oi~~');
  }
}

@Component({
  selector: 'app-parent',
  template: `
    <h3>Daddy say</h3>
    <button (click)="say()" >Say</button>
    Kid say: {{sonMess}}
  `
})
export class AppParentComponent {

  sonMess = '';
  constructor(private appService: AppService) {

    appService.childSaid$.subscribe(mess => {
      this.sonMess = mess;
    });
  }

  say() {
    this.appService.parentSay('con oi~~');
  }
};

import { NgModule }      from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { AppComponent,AppChildComponent,AppParentComponent} from './app.component';
import { AppService} from './app.service';
import { HttpModule } from '@angular/http';


@NgModule({
  imports: [
    BrowserModule,
    HttpModule
  ],
  declarations: [
    AppComponent,
    AppChildComponent,
    AppParentComponent
  ],
  providers: [],
  bootstrap: [ AppComponent ]
})
export class AppModule { }

h1 {
  font-size: 1.2em;
  color: #999;
  margin-bottom: 0;
}
h2 {
  font-size: 2em;
  margin-top: 0;
  padding-top: 0;
}
nav a {
  padding: 5px 10px;
  text-decoration: none;
  margin-top: 10px;
  display: inline-block;
  background-color: #eee;
  border-radius: 4px;
}
nav a:visited, a:link {
  color: #607D8B;
}
nav a:hover {
  color: #039be5;
  background-color: #CFD8DC;
}
nav a.active {
  color: #039be5;
}

import { platformBrowserDynamic } from '@angular/platform-browser-dynamic';

import { AppModule } from './app/app.module';

platformBrowserDynamic().bootstrapModule(AppModule);


/*
Copyright 2017 Google Inc. All Rights Reserved.
Use of this source code is governed by an MIT-style license that
can be found in the LICENSE file at http://angular.io/license
*/

/* Master Styles */
h1 {
  color: #369;
  font-family: Arial, Helvetica, sans-serif;
  font-size: 250%;
}
h2, h3 {
  color: #444;
  font-family: Arial, Helvetica, sans-serif;
  font-weight: lighter;
}
body {
  margin: 2em;
}
body, input[text], button {
  color: #888;
  font-family: Cambria, Georgia;
}
a {
  cursor: pointer;
  cursor: hand;
}
button {
  font-family: Arial;
  background-color: #eee;
  border: none;
  padding: 5px 10px;
  border-radius: 4px;
  cursor: pointer;
  cursor: hand;
}
button:hover {
  background-color: #cfd8dc;
}
button:disabled {
  background-color: #eee;
  color: #aaa;
  cursor: auto;
}

/* Navigation link styles */
nav a {
  padding: 5px 10px;
  text-decoration: none;
  margin-right: 10px;
  margin-top: 10px;
  display: inline-block;
  background-color: #eee;
  border-radius: 4px;
}
nav a:visited, a:link {
  color: #607D8B;
}
nav a:hover {
  color: #039be5;
  background-color: #CFD8DC;
}
nav a.active {
  color: #039be5;
}

/* items class */
.items {
  margin: 0 0 2em 0;
  list-style-type: none;
  padding: 0;
  width: 24em;
}
.items li {
  cursor: pointer;
  position: relative;
  left: 0;
  background-color: #EEE;
  margin: .5em;
  padding: .3em 0;
  height: 1.6em;
  border-radius: 4px;
}
.items li:hover {
  color: #607D8B;
  background-color: #DDD;
  left: .1em;
}
.items li.selected {
  background-color: #CFD8DC;
  color: white;
}
.items li.selected:hover {
  background-color: #BBD8DC;
}
.items .text {
  position: relative;
  top: -3px;
}
.items .badge {
  display: inline-block;
  font-size: small;
  color: white;
  padding: 0.8em 0.7em 0 0.7em;
  background-color: #607D8B;
  line-height: 1em;
  position: relative;
  left: -1px;
  top: -4px;
  height: 1.8em;
  margin-right: .8em;
  border-radius: 4px 0 0 4px;
}
/* everywhere else */
* {
  font-family: Arial, Helvetica, sans-serif;
}

<!DOCTYPE html>
<html>
  <head>
    <script>document.write('<base href="' + document.location + '" />');</script>
    <title>Angular Tour of Heroes</title>
    <meta name="viewport" content="width=device-width, initial-scale=1">

    <link rel="stylesheet" href="styles.css">

    <!-- Polyfills -->
    <script src="https://unpkg.com/core-js/client/shim.min.js"></script>

    <script src="https://unpkg.com/zone.js@0.7.4?main=browser"></script>
    <script src="https://unpkg.com/systemjs@0.19.39/dist/system.src.js"></script>

    <script src="systemjs.config.js"></script>
    <script>
      System.import('main.js').catch(function(err){ console.error(err); });
    </script>
  </head>

  <body>
    <my-app>Loading...</my-app>
  </body>
</html>

/**
 * WEB ANGULAR VERSION
 * (based on systemjs.config.js in angular.io)
 * System configuration for Angular samples
 * Adjust as necessary for your application needs.
 */
(function (global) {
  System.config({
    // DEMO ONLY! REAL CODE SHOULD NOT TRANSPILE IN THE BROWSER
    transpiler: 'ts',
    typescriptOptions: {
      // Copy of compiler options in standard tsconfig.json
      "target": "es5",
      "module": "commonjs",
      "moduleResolution": "node",
      "sourceMap": true,
      "emitDecoratorMetadata": true,
      "experimentalDecorators": true,
      "lib": ["es2015", "dom"],
      "noImplicitAny": true,
      "suppressImplicitAnyIndexErrors": true
    },
    meta: {
      'typescript': {
        "exports": "ts"
      }
    },
    paths: {
      // paths serve as alias
      'npm:': 'https://unpkg.com/'
    },
    // map tells the System loader where to look for things
    map: {
      // our app is within the app folder
      app: 'app',

      // angular bundles
      '@angular/core': 'npm:@angular/core/bundles/core.umd.js',
      '@angular/common': 'npm:@angular/common/bundles/common.umd.js',
      '@angular/compiler': 'npm:@angular/compiler/bundles/compiler.umd.js',
      '@angular/platform-browser': 'npm:@angular/platform-browser/bundles/platform-browser.umd.js',
      '@angular/platform-browser-dynamic': 'npm:@angular/platform-browser-dynamic/bundles/platform-browser-dynamic.umd.js',
      '@angular/http': 'npm:@angular/http/bundles/http.umd.js',
      '@angular/router': 'npm:@angular/router/bundles/router.umd.js',
      '@angular/router/upgrade': 'npm:@angular/router/bundles/router-upgrade.umd.js',
      '@angular/forms': 'npm:@angular/forms/bundles/forms.umd.js',
      '@angular/upgrade': 'npm:@angular/upgrade/bundles/upgrade.umd.js',
      '@angular/upgrade/static': 'npm:@angular/upgrade/bundles/upgrade-static.umd.js',

      // other libraries
      'rxjs':                      'npm:rxjs@5.0.1',
      'angular-in-memory-web-api': 'npm:angular-in-memory-web-api/bundles/in-memory-web-api.umd.js',
      'ts':                        'npm:plugin-typescript@5.2.7/lib/plugin.js',
      'typescript':                'npm:typescript@2.0.10/lib/typescript.js',

    },
    // packages tells the System loader how to load when no filename and/or no extension
    packages: {
      app: {
        main: './main.ts',
        defaultExtension: 'ts'
      },
      rxjs: {
        defaultExtension: 'js'
      }
    }
  });

})(this);

/*
Copyright 2016 Google Inc. All Rights Reserved.
Use of this source code is governed by an MIT-style license that
can be found in the LICENSE file at http://angular.io/license
*/

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

@Injectable()
export class AppService {

  private parentSaySource = new Subject<string>();
  private childSaySource = new Subject<string>();
  
  parentSaid$ = this.parentSaySource.asObservable();
  childSaid$ = this.childSaySource.asObservable();
  parentSay(message: string) {
    this.parentSaySource.next(message);
  }
  childSay(message: string) {
    this.childSaySource.next(message);
  }
}