Angular 5 firebase 数据库获得一项

Question

我有很多项目：

export class Project {
  $key: string;
  file: File;
  name: string;
  title: string;
  cat: string;
  url: string;
  progress: number;
  createdAt: Date = new Date();

  constructor(file: File) {
    this.file = file;
  }
}

我把它们都上传到：

  uploads: Observable<Project[]>;

  private saveFileData(upload: Project) {
    this.db.list(`profile/${this.auth.userId}/project`).push(upload);
}

然后我想得到一个：

 uploads: Observable<Project[]>;
getOne(){
  this.uploads = this.db.list(`profile/${this.auth.userId}/project/${this.projectId}`);
}

在这种情况下，我在 this.uploads 上收到错误

（Angularfirelist 不能分配给 Observable。）

然后我尝试了这个：

  uploads: AngularFireList<Project[]>;

getOne(){
  this.uploads = this.db.list(`profile/${this.auth.userId}/project/${this.projectId}`);
}

错误：

错误错误: InvalidPipeArgument: '[object Object]' 用于管道 '异步管道'

如何获得那个项目？

Answer 1

添加valueChanges()只获取数据，或添加snapshotChanges()获取数据的有效负载：

this.uploads = this.db.list(`profile/${this.auth.userId}/project/${this.projectId}`).valueChanges();