Angular : Http Service and Observables

<!DOCTYPE html>
<html>

  <head>
    <base href="." />
    <script type="text/javascript" charset="utf-8">
      window.AngularVersionForThisPlunker = 'latest'
    </script>
    <title>angular playground</title>
    <link rel="stylesheet" href="style.css" />
    <script src="https://unpkg.com/core-js@2.4.1/client/shim.min.js"></script>
    <script src="https://unpkg.com/zone.js/dist/zone.js"></script>
    <script src="https://unpkg.com/zone.js/dist/long-stack-trace-zone.js"></script>
    <script src="https://unpkg.com/reflect-metadata@0.1.3/Reflect.js"></script>
    <script src="https://unpkg.com/systemjs@0.19.31/dist/system.js"></script>
    <script src="config.js"></script>
    <script>
    System.import('app')
      .catch(console.error.bind(console));
  </script>
  </head>

  <body>
    <div>This example is a part of the tutorial - <a href="https://angularbytes.witspry.com/2017/09/angular-5-consuming-restful-service-with-httpclient-rxjs.html">	
https://angularbytes.witspry.com/2017/09/angular-5-consuming-restful-service-with-httpclient-rxjs.html</a> </div>
    <div style="margin-bottom:20px;"></div>
    <div style="text-align:center;border-bottom-style:solid;"></div>
    <div style="margin-bottom:20px;"></div>
    <my-app>
    loading...
  </my-app>
  </body>

</html>

/* Styles go here */

### Angular Starter Plunker - Typescript

var angularVersion = '@5.0.0'; 

System.config({
  //use typescript for compilation
  transpiler: 'typescript',
  //typescript compiler options
  typescriptOptions: {
    emitDecoratorMetadata: true
  },
  paths: {
    'npm:': 'https://unpkg.com/'
  },
  //map tells the System loader where to look for things
  map: {
    
    'app': './src',
    '@angular/core': 'npm:@angular/core'+ angularVersion + '/bundles/core.umd.js',
    '@angular/common': 'npm:@angular/common' + angularVersion + '/bundles/common.umd.js',
    '@angular/common/http': 'npm:@angular/common' + angularVersion + '/bundles/common-http.umd.js',
    '@angular/compiler': 'npm:@angular/compiler' + angularVersion  + '/bundles/compiler.umd.js',
    '@angular/platform-browser': 'npm:@angular/platform-browser' + angularVersion + '/bundles/platform-browser.umd.js',
    '@angular/platform-browser-dynamic': 'npm:@angular/platform-browser-dynamic' + angularVersion + '/bundles/platform-browser-dynamic.umd.js',
    '@angular/http': 'npm:@angular/http' + angularVersion + '/bundles/http.umd.js',
    '@angular/router': 'npm:@angular/router' + angularVersion +'/bundles/router.umd.js',
    '@angular/forms': 'npm:@angular/forms' + angularVersion + '/bundles/forms.umd.js',
    '@angular/animations': 'npm:@angular/animations' + angularVersion + '/bundles/animations.umd.js',
    '@angular/platform-browser/animations': 'npm:@angular/platform-browser' + angularVersion + '/bundles/platform-browser-animations.umd.js',
    '@angular/animations/browser': 'npm:@angular/animations' + angularVersion + '/bundles/animations-browser.umd.js',
    
    '@angular/core/testing': 'npm:@angular/core' + angularVersion + '/bundles/core-testing.umd.js',
    '@angular/common/testing': 'npm:@angular/common' + angularVersion + '/bundles/common-testing.umd.js',
    '@angular/common/http/testing': 'npm:@angular/common' + angularVersion + '/bundles/common-http-testing.umd.js',
    '@angular/compiler/testing': 'npm:@angular/compiler' + angularVersion + '/bundles/compiler-testing.umd.js',
    '@angular/platform-browser/testing': 'npm:@angular/platform-browser' + angularVersion + '/bundles/platform-browser-testing.umd.js',
    '@angular/platform-browser-dynamic/testing': 'npm:@angular/platform-browser-dynamic' + angularVersion + '/bundles/platform-browser-dynamic-testing.umd.js',
    '@angular/http/testing': 'npm:@angular/http' + angularVersion + '/bundles/http-testing.umd.js',
    '@angular/router/testing': 'npm:@angular/router' + angularVersion + '/bundles/router-testing.umd.js',
    'tslib': 'npm:tslib@1.6.1',
    'rxjs': 'npm:rxjs@5.0.0',
    'typescript': 'npm:typescript@2.2.1/lib/typescript.js'
  },
  //packages defines our app package
  packages: {
    app: {
      main: './main.ts',
      defaultExtension: 'ts'
    },
    rxjs: {
      main: 'index.js',
      map:{
        './operators' : './operators/index.js'
      },
      defaultExtension: ''
    }
  }
});

//main entry point
import {platformBrowserDynamic} from '@angular/platform-browser-dynamic';
import {AppModule} from './app';

platformBrowserDynamic().bootstrapModule(AppModule)

//our root app component
import {Component, NgModule} from '@angular/core'
import {BrowserModule} from '@angular/platform-browser'
import { HttpClientModule } from '@angular/common/http';
import 'rxjs/Rx'

import {Survey} from './survey'
import {SurveyService} from './survey.service';

@Component({
  selector: 'my-app',
  template: `
    <div>
      <survey></survey>
    </div>
  `,
})
export class App {
  name:string; 
  constructor() {
    this.name = 'Angular'
  }
}

@NgModule({
  imports: [ BrowserModule, HttpClientModule ],
  declarations: [ App, Survey ],
  providers:[SurveyService],
  bootstrap: [ App ]
})
export class AppModule {}

import {Injectable} from '@angular/core'
import {HttpClient, HttpErrorResponse } from '@angular/common/http'
import {Observable} from 'rxjs/Observable'
import 'rxjs/add/operator/catch';
import 'rxjs/add/operator/do';
import 'rxjs/add/operator/map';

import {ISurvey} from './isurvey'

@Injectable()
export class SurveyService {
  constructor(private _http:HttpClient){
    
  }
  
  getSurveyQuestion(): Observable<ISurvey[]>{
    return this._http
      .get<ISurvey[]>('./src/survey.json')
      .do(data =>console.log('All : ' + JSON.stringify(data)))
      .catch(this.handleError);
  }
  
  private handleError(error: HttpErrorResponse)
  {
    debugger;
    console.error(error);
    let errorMessage = '';
    if (err.error instanceof Error) {
        // A client-side or network error occurred. Handle it accordingly.
        errorMessage = `An error occurred: ${err.error.message}`;
    } else {
        // The backend returned an unsuccessful response code.
        // The response body may contain clues as to what went wrong,
        errorMessage = `Server returned code: ${err.status}, error message is: ${err.message}`;
    }
    console.error(errorMessage);
    return Observable.throw(errorMessage);
}

import {Component, Injectable} from '@angular/core'
import {ISurvey} from './isurvey'
import {SurveyService} from './survey.service';

@Component({
  selector: 'survey',
  template: `
    <div>
      <h2>Question : </h2>
      <div *ngIf="MySurvey && MySurvey.length">
      <div *ngFor="let survey of MySurvey; let idx = index"><br/>
        <div>{{survey.question}}</div>
        <div *ngFor="let choice of survey.choices">
          <input type="radio" name="radioGroup{{idx}}"/>{{choice}}
        </div>
      </div>
      </div>
    </div>
  `
})
export class Survey implements OnInit{
  MySurvey : ISurvey[] = [];
  constructor(private _surveyService: SurveyService){
   
  }
  
  ngOnInit(){
    this._surveyService.getSurveyQuestion().subscribe(data => {
        console.log(data);
        this.MySurvey = data;
        }, err => {
          console.log(err);
        });
  }
}


export interface ISurvey{
 question:string;
 choices: string[];
}

[
    {
        "question": "What is your favourite programming language?",
        "choices": ["Swift","Python","Objective-C","Ruby"]
    },
    {
        "question": "What is your major learning source?",
        "choices": ["Books","Online Tutorials","Online Bootcamp courses"]
    }
]