从回调中创建一个Observable

Question

我有一个auth防护,当访问该站点并且用户已经登录时,需要异步响应true/false.

我正在使用Firebase onAuthStateChanged(链接到文档),它使用回调函数.如何将我的isLoggedIn()方法变成可以返回的东西Observable<boolean>？

Typscript:

get isLoggedIn(): Observable<boolean> {

    // want something like this:
    return Observable.fromCallback(firebase.auth().onAuthStateChanged).map(user => !!user);

    // this returns () => boolean, but I need a promise or observable
    return firebase
      .auth()
      .onAuthStateChanged((user) => {
        return !!user;
      });

}

Answer 1

还有一种方法可以使用来自 rxjs/observable/bindCallback 的 bindCallback

const observable=bindCallback(functionWhichExpectsCallBack)

例如

function foo(value, callback) {
  callback(value);
}
//converts callback to observable
    const observable = bindCallback(foo); 
    observable(1)
      .subscribe(console.log); 

Answer 2

你可以这样做.

get isLoggedIn(): Observable<boolean> {

  // want something like this:
  return Observable.create(
    observer => firebase
        .auth()
        .onAuthStateChanged((user) => {
          observer.next(!!user)
        });
    );
}

Answer 3

注意：bindCallback已Observable.create弃用，
您可以使用new Observable：

...
return new Observable((subscriber) => {
  firebase
    .auth()
    .onAuthStateChanged((user) => {
      subscriber.next(user);
    })
}