ng-2 angular lifecycle

import {Component} from '@angular/core';
import {DemoService} from './demo.service';
 
@Component({
  selector: 'demo-app',
  template:`
  <h1>Angular2 HTTP Demo App</h1>
  <h2>Foods</h2>
  <div *ngIf="foods_error">An error occurred while loading the foods!</div>
  <ul>
    <li *ngFor="let food of foods">{{food.name}}</li>
  </ul>
  ...
  `
})
export class AppComponent {
 
  ...
  public foods_error:Boolean = false;
 
  constructor(private _demoService: DemoService) { }
 
  ...
 
  getFoods() {
    this._demoService.getFoods().subscribe(
      data => { this.foods = data},
      err => { this.foods_error = true }
    );
  }
 
  getBooksAndMovies() {
    this._demoService.getBooksAndMovies().subscribe(
      data => {
        this.books = data[0]
        this.movies = data[1]
      }
    );
  }
}