Olá.

Estou seguindo o exemplo do professor quanto à iteração das fotos do componente inseridos na diretiva ngFor mas ele está reclamando erro no array photos declarado dentro do app.component.html, dizendo: "[Angular] Identifier 'photos' is not defined. The component declaration, template variable declarations, and element references do not contain such a member".

Segue o código do app.component.html e do ap.component.ts:

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

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

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

  photos = [
    {
      url: 'https://upload.wikimedia.org/wikipedia/commons/thumb/5/5a/Sultan_the_Barbary_Lion.jpg/440px-Sultan_the_Barbary_Lion.jpg',
      description: 'Leão'
    },
    {
      url: 'https://upload.wikimedia.org/wikipedia/commons/thumb/2/2d/Lioness_Etosha_NP.jpg/500px-Lioness_Etosha_NP.jpg',
      description: 'Leoa'
    }
  ];

}