title: Adding an array of artists to 1 festival doesn't work
body: <p>I'm trying to add an array of different types of artists to a festival which will the be displayed on the page. Festivals have their own model, and so do artists. </p>
  
  <p>This is the artist model:</p>
  
  <pre><code>export class Artist{
      // public _id: string;
      public name: string;
      public genre: string;
  
      constructor(name: string, genre: string){
          // this._id = _id;
          this.name = name;
          this.genre = genre;
      }
  }
  </code></pre>
  
  <p>The festival model: </p>
  
  <pre><code>import { Artist } from './artist.model';
  
  export class Festival{
      // public _id: string;
      public name: string;
      public genre: string;
      public description: string;
      public location: string;
      public imageUrl: string;
      public price: number;
      public artist: Artist;
  
      constructor( name: string, genre: string, description: string, location: string, imageurl: string, price: number, artist: Artist)
      {
          // this._id = _id;
          this.name = name;
          this.genre = genre;
          this.description = description;
          this.location = location;
          this.imageUrl = imageurl;
          this.price = price;
          this.artist = artist;
      }
  }
  </code></pre>
  
  <p>The festival service that creates these new instances of festival for now:</p>
  
  <pre><code>import { Festival } from 'src/app/models/festival.model';
  import { EventEmitter } from '@angular/core';
  import { Artist } from 'src/app/models/artist.model';
  
  export class FestivalService{
      festivalSelected = new EventEmitter&lt;Festival&gt;();
  
      private festivals: Festival[] = [
          new Festival('DGTL', 'Techno', 'Test description', 'Amsterdam', 'https://festivalfans.nl/wp-content/uploads/2014/11/dgtl-2017.jpg', 45, [] ),
          new Festival('RR', 'Techno', 'Party', 'Rotterdam', 'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAOEAAADhCAMAAAAJbSJIAAAAeFBMVEUAAAD////6+vodHR3', 45)
        ];
  
        getFestivals() {
            return this.festivals.slice();
        }
        addFestivalsToFavorites(festival: Festival[]){
  
        }
  }
  </code></pre>