给 BehaviorSubject 初始值 - 值是一个 Observable [英] Give BehaviorSubject initial value - value being an Observable

问题描述

我知道我不能给 BehaviorSubject 一个 Observable 值，但我需要一种方法来解决这个问题.在应用程序初始化时，我正在获取当前用户(如果存在)，并且我需要为 BehaviorSubject 提供该潜在值.所以我的服务代码是这样的:

I know that I cannot give BehaviorSubject an Observable value, but I need a way to solve this issue. On app initialization I am fetching current user (if exists), and I need to give the BehaviorSubject that potential value. So my service code looks like this:

private user = new BehaviorSubject<User>(this.getUser());
public user$ = this.user.asObservable();

getUser(): User {
  // does obviously not work!
  return this.apiService.getUser()
    .map(data => {
      if(data) {
        return data;
      }
      // do something else
    })  
}

那么是否有一些神奇的 rxjs 操作符可以解决这个问题，或者其他一些可能性?

So is there some magical rxjs operator to solve this issue, or some other possibility?

提前致谢！

推荐答案

我愿意这样做

private user = new BehaviorSubject<User>(null);
public user$ = this.user.asObservable();

constructor() {
  this.getUser();
}

getUser(): User {
  // does obviously not work!
  return this.apiService.getUser()
    .subscribe(data => {
      if(!!data) {
        this.user.next(data); // <<== added
      }
      // do something else
    })  
}

这篇关于给 BehaviorSubject 初始值 - 值是一个 Observable的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！