Question

我想计算从我的Firebase数据库作为可观察项返回的一组项目的总价。但是，该服务不会返回任何内容。

这是我尝试的内容：

服务

  getRooms(): any {
    let result = {};
    this.items
      .toPromise()
      .then(items => {
        for (let item of items) {
          let name = item.name;
          let price = item.price;
          if (name in result) {
            result[name] += price;
          } else {
            result[name] = price;
          }
        }
      });
    return result;
  }

组件

export class InspirationComponent implements OnInit {

  rooms: any;

  constructor(private inspirationService: InspirationService) {
    this.items = this.inspirationService.getRooms();
  }

  ngOnInit() {
  }

}

Answer 1

对于初学者来说，你不应该像这样填充变量this.items。你应该这样做：

<强>组件

export class InspirationComponent implements OnInit {

  rooms: any;

  constructor(private inspirationService: InspirationService) {
    this.inspirationService.getRooms().then(result => {
         this.items = result ;
    });
  }

<强>服务

 getRooms(): any {
    return this.http.get('url')
      .map(items => {
         let result = {}
         for (let item of items) {
          let name = item.name;
          let price = item.price;
          if (name in result) {
            result[name] += price;
          } else {
            result[name] = price;
          }
        }
         return = result ;
    }).toPromise();
  }

Answer 2

我认为你必须解决你的承诺。更改组件。

export class InspirationComponent implements OnInit {

 rooms: any;

  constructor(private inspirationService: InspirationService) {
    this.items = this.inspirationService.getRooms((result) => {console.log(result);});
  }
  ngOnInit() {
  }

}

将observable转换为promise并操纵结果

2 个答案: