undefined 不可迭代（无法读取属性 Symbol(Symbol.iterator)）

Question

我正在尝试遍历文件列表以执行删除查询。首先，我从属性"postnumber"=user 输入的数据库中的表“文件”中获取数据。然后将其保存到“fileList:Files[]”中。然后循环通过此 fileList 以执行删除查询。但它一直在说

"ERROR TypeError: undefined is not iterable (cannot read property Symbol(Symbol.iterator))”。见这张图 =>

forum-admin-list.component.ts

import { FileService } from 'src/app/shared/file.service';
import { Files } from 'src/app/shared/files.model';
export class ForumAdminListComponent {
fileList:Files[];
onDelete(pNo:string){ 
        this.fservice.getPost(pNo).subscribe(actionArray => {
          this.fileList = actionArray.map(item => {
            return {
              id: item.payload.doc.id,
              ...item.payload.doc.data()
            } as Files;
          })
        });
        for(let i of this.fileList){
          this.storage.storage.refFromURL(i.path).delete();
          this.firestore.doc("files/"+i.id).delete();
        }
  }
}

files.model.ts

export class Files {
    id:string;
    pNo:string;
    downloadURL:string;
    path:string;
}

file.service.ts

export class FileService {
    formData: Files; 
    constructor(private firestore: AngularFirestore) { }

    getPost(userRef){
      return this.firestore.collection('files',ref=>ref.where('pNo','==',userRef)).snapshotChanges();
    }
}

Answer 1

您在 subscribe() 之外循环访问 fileList，这意味着它实际上不会等待 Observable 被解析。尝试在您的subscribe() 内循环。

onDelete(pNo:string){ 
  this.fservice.getPost(pNo).subscribe(actionArray => {
    this.fileList = actionArray.map(item => {
      return {
        id: item.payload.doc.id,
        ...item.payload.doc.data()
      } as Files[];

      for(let i of this.fileList){
        this.storage.storage.refFromURL(i.path).delete();
        this.firestore.doc("files/"+i.id).delete();
      }
    })
  });
}

另外，您可能想标记订阅结果as Files[] 而不是as File