<!DOCTYPE html>
<html>

  <head>
    <title>Angular 2+ Observable Data Services</title>
    <script src="https://unpkg.com/core-js/client/shim.min.js"></script>
    <script src="https://unpkg.com/zone.js@0.8.4?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>
    <style>
      body {
        font-family: "HelveticaNeue-Light", "Helvetica Neue Light", "Helvetica Neue", Helvetica, Arial, "Lucida Grande", sans-serif; 
        font-weight: 300;
      }
    </style>
  </head>

  <body>
    <todo-app>Loading...</todo-app>
  </body>
</html>
A plunker demonstration Observable Data Services in Angular 2

https://coryrylan.com/blog/angular-2-observable-data-services
import { Component } from '@angular/core';
import { FormBuilder, Validators } from '@angular/common';

import { TodoComponent } from 'app/todo.component';
import { TodoService } from 'app/todo.service';

@Component({
  selector: 'todo-app',
  template: `
    <p>Only implimented a simple post and delete</p>
    
    <h3>Component 1</h3>
    <todo-component></todo-component>
    
    <br /><br />
    
    <h3>Component 2</h3>
    <todo-component></todo-component>
  `
})
export class AppComponent {
  constructor() { }
}
import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { ReactiveFormsModule } from '@angular/forms';
import { RouterModule } from '@angular/router';
import { HttpClientModule } from '@angular/common/http';

import { AppComponent } from './app.component';
import { TodoComponent } from './todo.component';
import { TodoService } from './todo.service';

@NgModule({
  imports: [
    BrowserModule,
    ReactiveFormsModule,
    HttpClientModule
  ],
  declarations: [
    TodoComponent,
    AppComponent
  ],
  providers: [ TodoService ],
  bootstrap: [ AppComponent ]
})
export class AppModule {
}
import { platformBrowserDynamic } from '@angular/platform-browser-dynamic';

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

const platform = platformBrowserDynamic();
platform.bootstrapModule(AppModule);
import { Component } from '@angular/core';
import { FormBuilder, Validators} from '@angular/forms';
import { map } from 'rxjs/operators';

import { TodoService } from 'app/todo.service';

@Component({
  selector: 'todo-component',
  template: `
    <div>
      <form [formGroup]="todoForm" (submit)="onSubmit()">
         <button>Add Item</button><br />
      </form>
      
      <p>
        {{singleTodo$ | async | json}}
      </p>
      
      <div *ngFor="let todo of todos | async">
        {{ todo.value }} <button (click)="deleteTodo(todo.id)">x</button>
      </div>
    </div>
  `
})
export class TodoComponent {
  todos: Observable<Todo[]>;
  singleTodo$: Observable<Todo>;
  
  constructor(
    private todoService: TodoService, 
    private formBuilder: FormBuilder) {
      
    this.todoForm = this.formBuilder.group({
      'todo': ['', Validators.required]
    });
  }
  
  ngOnInit() {
    this.todos = this.todoService.todos;
    this.singleTodo$ = this.todoService.todos.pipe(
      map(todos => todos.find(item => item.id === '1'))
    );
    
    this.todoService.loadAll();
    this.todoService.load('1');
  }
  
  onSubmit() {
    this.todoService.create({ value: this.todoForm.controls.todo.value });
  }
  
  deleteTodo(todoId: number) {
    this.todoService.remove(todoId);
  }
}
import { Injectable } from '@angular/core';
import { HttpClient } from '@angular/common/http';
import { Observable } from 'rxjs/Observable';
import { BehaviorSubject } from 'rxjs/BehaviorSubject';

export interface Todo {
  id: number | string;
  createdAt: number;
  value: string;
}

@Injectable()
export class TodoService {
  todos: Observable<Todo[]>
  private _todos: BehaviorSubject<Todo[]>;
  private baseUrl: string;
  private dataStore: {
    todos: Todo[]
  };

  constructor(private http: HttpClient) {
    this.baseUrl = 'https://56e05c3213da80110013eba3.mockapi.io/api';
    this.dataStore = { todos: [] };
    this._todos = <BehaviorSubject<Todo[]>>new BehaviorSubject([]);
    this.todos = this._todos.asObservable();
  }

  loadAll() {
    this.http.get(`${this.baseUrl}/todos`).subscribe(data => {
      this.dataStore.todos = data;
      this._todos.next(Object.assign({}, this.dataStore).todos);
    }, error => console.log('Could not load todos.'));
  }

  load(id: number | string) {
    this.http.get(`${this.baseUrl}/todos/${id}`).subscribe(data => {
      let notFound = true;

      this.dataStore.todos.forEach((item, index) => {
        if (item.id === data.id) {
          this.dataStore.todos[index] = data;
          notFound = false;
        }
      });

      if (notFound) {
        this.dataStore.todos.push(data);
      }

      this._todos.next(Object.assign({}, this.dataStore).todos);
    }, error => console.log('Could not load todo.'));
  }

  create(todo: Todo) {
    this.http.post(`${this.baseUrl}/todos`, JSON.stringify(todo)).subscribe(data => {
        this.dataStore.todos.push(data);
        this._todos.next(Object.assign({}, this.dataStore).todos);
      }, error => console.log('Could not create todo.'));
  }

  update(todo: Todo) {
    this.http.put(`${this.baseUrl}/todos/${todo.id}`, JSON.stringify(todo)).subscribe(data => {
        this.dataStore.todos.forEach((t, i) => {
          if (t.id === data.id) { this.dataStore.todos[i] = data; }
        });

        this._todos.next(Object.assign({}, this.dataStore).todos);
      }, error => console.log('Could not update todo.'));
  }

  remove(todoId: number) {
    this.http.delete(`${this.baseUrl}/todos/${todoId}`).subscribe(response => {
      this.dataStore.todos.forEach((t, i) => {
        if (t.id === todoId) { this.dataStore.todos.splice(i, 1); }
      });

      this._todos.next(Object.assign({}, this.dataStore).todos);
    }, error => console.log('Could not delete todo.'));
  }
}
/**
 * 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/animations': 'npm:@angular/animations/bundles/animations.umd.js',
      '@angular/animations/browser': 'npm:@angular/animations/bundles/animations-browser.umd.js',
      '@angular/core': 'npm:@angular/core/bundles/core.umd.js',
      '@angular/common': 'npm:@angular/common/bundles/common.umd.js',
      '@angular/common/http': 'npm:@angular/common/bundles/common-http.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/animations': 'npm:@angular/platform-browser/bundles/platform-browser-animations.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@5.5.2',
      'rxjs/operators':            'npm:rxjs@5.5.2/operators/index.js',
      'tslib':                     'npm:tslib/tslib.js',
      'angular-in-memory-web-api': 'npm:angular-in-memory-web-api@0.4/bundles/in-memory-web-api.umd.js',
      'ts':                        'npm:plugin-typescript@5.2.7/lib/plugin.js',
      'typescript':                'npm:typescript@2.4.2/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',
        meta: {
          './*.ts': {
            loader: 'systemjs-angular-loader.js'
          }
        }
      },
      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
*/
{
  "compilerOptions": {
    "target": "es5",
    "module": "commonjs",
    "moduleResolution": "node",
    "sourceMap": true,
    "emitDecoratorMetadata": true,
    "experimentalDecorators": true,
    "removeComments": false,
    "noImplicitAny": true,
    "suppressImplicitAnyIndexErrors": true
  }
}
var templateUrlRegex = /templateUrl\s*:(\s*['"`](.*?)['"`]\s*)/gm;
var stylesRegex = /styleUrls *:(\s*\[[^\]]*?\])/g;
var stringRegex = /(['`"])((?:[^\\]\\\1|.)*?)\1/g;

module.exports.translate = function(load){
  if (load.source.indexOf('moduleId') != -1) return load;

  var url = document.createElement('a');
  url.href = load.address;

  var basePathParts = url.pathname.split('/');

  basePathParts.pop();
  var basePath = basePathParts.join('/');

  var baseHref = document.createElement('a');
  baseHref.href = this.baseURL;
  baseHref = baseHref.pathname;

  if (!baseHref.startsWith('/base/')) { // it is not karma
    basePath = basePath.replace(baseHref, '');
  }

  load.source = load.source
    .replace(templateUrlRegex, function(match, quote, url){
      var resolvedUrl = url;

      if (url.startsWith('.')) {
        resolvedUrl = basePath + url.substr(1);
      }

      return 'templateUrl: "' + resolvedUrl + '"';
    })
    .replace(stylesRegex, function(match, relativeUrls) {
      var urls = [];

      while ((match = stringRegex.exec(relativeUrls)) !== null) {
        if (match[2].startsWith('.')) {
          urls.push('"' + basePath + match[2].substr(1) + '"');
        } else {
          urls.push('"' + match[2] + '"');
        }
      }

      return "styleUrls: [" + urls.join(', ') + "]";
    });

  return load;
};