赋予BehaviorSubject初始值-值是可观察的 [英] Give BehaviorSubject initial value - value being an Observable

问题描述

我知道我不能给 BehaviorSubject 一个可观察的值，但是我需要一种解决此问题的方法.在应用初始化时，我正在获取当前用户(如果存在)，并且需要给 BehaviorSubject 这个潜在值.所以我的服务代码如下:

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，有没有神奇的rxjs运算符可以解决此问题，或者还有其他可能性?

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

提前谢谢！

推荐答案

我会这样做

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
    })  
}

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