Angular2 HTTP cache with rxJS

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

import { DataService } from './data.service';

@Component({
  selector: 'my-app',
  template: `<div (click)="getData()">getData from AppComponent</div>
            <child></child>
            `
})
export class AppComponent {
    constructor(private dataService: DataService) {}
    
    getData() {
        this.dataService.getData().subscribe(requestData => { 
            console.log('AppComponent', requestData);
      });
    }
}


@Component({
  selector: 'child',
  template: `<div (click)="getData()">getData from ChildComponent</div>`
})
export class ChildComponent { 
    constructor(private dataService: DataService) {}
    
    getData() {
        this.dataService.getData().subscribe(
          requestData => {
            console.log('ChildComponent', requestData);
          },
          // handle the error, otherwise will break the Observable
          error => console.log(error)
        );
    }
}


/*
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 { NgModule }      from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { HttpModule }    from '@angular/http';

import { AppComponent, ChildComponent }   from './app.component';
import { DataService } from './data.service';

@NgModule({
  imports:      [ BrowserModule, HttpModule ],
  declarations: [ AppComponent, ChildComponent ],
  providers: [ DataService ],
  bootstrap:    [ AppComponent ]
})

export class AppModule { }


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

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

const platform = platformBrowserDynamic();
platform.bootstrapModule(AppModule);


/*
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
*/

/* 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-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:hover {
  background-color: #BBD8DC;
  color: white;
}
.items .text {
  position: relative;
  top: -3px;
}
.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;
}

my-app div {
    background: #eeeeee;
    color: black;
    float: left;
    clear: both;
    padding: 20px;
    border-radius: 20px;
    cursor: pointer;
    margin: 20px;
}

my-app div:hover {
    background: green;
    color: white;
}

my-app div:active {
   background: yellow;
}


/*
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
*/

<!DOCTYPE html>
<html>
  <head>
    <title>Angular QuickStart</title>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <link rel="stylesheet" href="styles.css">

    <!-- 1. Load libraries -->
     <!-- Polyfill(s) for older browsers -->
    <script src="https://unpkg.com/core-js/client/shim.min.js"></script>

    <script src="https://unpkg.com/zone.js@0.6.25?main=browser"></script>
    <script src="https://unpkg.com/reflect-metadata@0.1.3"></script>
    <script src="https://unpkg.com/systemjs@0.19.27/dist/system.src.js"></script>

    <!-- 2. Configure SystemJS -->
    <script src="systemjs.config.js"></script>
    <script>
      System.import('app').catch(function(err){ console.error(err); });
    </script>
  </head>

  <!-- 3. Display the application -->
  <body>
    <my-app>Loading...</my-app>
  </body>
</html>


<!-- 
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
-->

### Angular Documentation Example 

QuickStart

/**
 * PLUNKER 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: {
      tsconfig: 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/forms': 'npm:@angular/forms/bundles/forms.umd.js',
      '@angular/upgrade': 'npm:@angular/upgrade/bundles/upgrade.umd.js',

      // other libraries
      'rxjs':                       'npm:rxjs',
      'angular2-in-memory-web-api': 'npm:angular2-in-memory-web-api',
      'ts':                         'npm:plugin-typescript@4.0.10/lib/plugin.js',
      'typescript':                 'npm:typescript@2.0.2/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'
      },
      'angular2-in-memory-web-api': {
        main: './index.js',
        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
*/

{
  "compilerOptions": {
    "target": "es5",
    "module": "commonjs",
    "moduleResolution": "node",
    "sourceMap": true,
    "emitDecoratorMetadata": true,
    "experimentalDecorators": true,
    "removeComments": false,
    "noImplicitAny": true,
    "suppressImplicitAnyIndexErrors": true
  }
}

import { Injectable } from '@angular/core';
import { Http } from '@angular/http';
import { ReplaySubject } from 'rxjs/Rx';

@Injectable()
export class DataService {
    private dataObs$ = new ReplaySubject(1);
    
    constructor(private http: Http) { }

    getData(forceRefresh?: boolean) {
        // If the Subject was NOT subscribed before OR if forceRefresh is requested 
        if (!this.dataObs$.observers.length || forceRefresh) {
            this.http.get('http://jsonplaceholder.typicode.com/posts/2').subscribe(
                data => this.dataObs$.next(data),
                error => {
                    this.dataObs$.error(error);
                    // Recreate the Observable as after Error we cannot emit data anymore
                    this.dataObs$ = new ReplaySubject(1);
                }
            );
        }

        return this.dataObs$;
    }
}