Não exibe nada na página. | Angular parte 1: produtividade e organização com framework SPA

import { Component } from '@angular/core';

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css']
})
export class AppComponent {

  photos = [
    {
    url: 'https://http2.mlstatic.com/patins-rollerblade-twister-edge-110-3wd-D_NQ_NP_793209-MLB27800138670_072018-F.jpg',
    description: 'Patins'
    },
    {
    url: 'https://http2.mlstatic.com/patins-rollerblade-twister-edge-110-3wd-D_NQ_NP_793209-MLB27800138670_072018-F.jpg',
    description: 'Patins'
    }
  ];
}


<ap-photo
    *ngFor="let photo of photos"
    [url]= "photo.url"
    [description]="photo.description">
</ap-photo>