將背景圖像與ngStyle一起使用將返回undefined

Question

我嘗試添加圖像（使用API​​加載項目）作為元素的背景圖像 。 但是，它保持Cannot read property 'url' of undefined錯誤的Cannot read property 'url' of undefined 。 雖然它實際上會呈現url。 這是模板方面：

 <div class="col s12 m4" *ngFor="let partner of partners">
                <div class="card" *ngIf='partner'>
                    <div class="card-image " [ngStyle]="{'background-image': 'url(' + partner?.photo['url'] + ')'}">
                        <a class=" btn-floating halfway-fab waves-effect waves-light blue left ">
                            <i class="material-icons ">shopping_cart</i>
                        </a>
                        <a class="btn-floating halfway-fab red " [routerLink]='"/dashboard/partners/edit/"+partner["id"]'>
                            <i class="large material-icons ">mode_edit</i>
                        </a>
                    </div>
                    <div class="card-content ">
                        <h5 class="center font-weight-400 ">{{partner.name}}</h5>
                        <p class="center ">{{partner.category.name}}</p>
                    </div>
                </div>
  </div>

和控制器：

  export class PartnersListComponent implements OnInit {
    partners: {}[] = [];

    constructor(private _partnersService: PartnersService) {}

    ngOnInit() {
      this._partnersService.getPartners().subscribe(data => {
        if (data.status == "200") {
          this.partners = data.data;
        }
      });
    }
  }

示例數據：

category:'',
created_at:"2017-12-27 12:57:50",
deleted_at:null,
first_entry:1,
id:1,
name:"Zara",
photo:{id: 5, url: "example.jpeg"},
updated_at:"2017-12-27 12:57:50",
username:"zara-001"

Answer 1

根據錯誤消息，未為至少一個partner定義photo字段。 您可以使用elvis運算符防止這種情況：

[ngStyle]="{'background-image': `url(${partner?.photo?.url})`}"

要么

[style.background-image]="`url(${partner?.photo?.url})`"