将背景图像与ngStyle一起使用将返回undefined

Question

我尝试添加图像（使用API​​加载项目）作为元素的背景图像 。 但是，它保持Cannot read property 'url' of undefined错误的Cannot read property 'url' of undefined 。 虽然它实际上会呈现url。 这是模板方面：

 <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;
        }
      });
    }
  }

示例数据：

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

根据错误消息，未为至少一个partner定义photo字段。 您可以使用elvis运算符防止这种情况：

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

要么

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