Observable

• We finalize an observable stream by subscribing to it
• The subscribe method accepts three event handlers
• onNext is called when new data arrives
• onError is called when an error is thrown
• onComplete is called when the stream is completed

loadItems() {
 return this.http.get(BASE_URL);
}

export class ItemsComponent {
    items: Item[];
    selectedItem: Item;
    
    constructor(
        private itemsService: ItemsService
    ) {}
    
    getItems() {
        this.itemsService.loadItems()
        .subscribe((items: Item[]) => this.items = items);
    }
}