只运行一次 observables，然后检查是否完成 - angular2 typescript

Question

Very new to Observables so apologies if this is basic, but i have tried googling, and dont seem to be able to find what i want.

Here is an example plunkr, very basic.
https://plnkr.co/edit/kgECPQyoKqY7RamebUUu?p=preview

Why is my Initialized method not called until my service calls it? I thought that the initialized observable would be executed as soon as i do Observable.forkJoin ?? Do i need to start the process somehow?

And why my myService.loadOtherData method never seems to call the subscribe method???

Thanks in advance

Answer 1

If you're very new to Observables, i suggest you start with a basic example.

For example: (pseudo-code, maybe)

let observable = new Observable<string>(observer => {
  if (1 == 1) {
    observer.next("one is one");
  } else {
    observer.error("one is not one");
  }
});
observable.subscribe(
  response => console.log(response), 
  error -> console.log(error)
);

Using a subject is more of the same but a Subject can be used a little more freely:

let subject = new Subject();
subject.subscribe(response -> console.log(response));
subject.next('hello');

I believe i saw you combinding the two, subscribing to the subject then getting data with an observable? With these examples, do you have enough information or do you need a very specific example?

edit:

your this.initialized.subscribe 'starts the process'. You call the loadOtherData function too late, which makes you NOT subscribed to this.initialized when the data returns. That's why you don't see console.log('initialized')

edit2:

Take note that a BehaviorSubject holds it's data and returns it on subscribe. There is no need to initialize it with an empty string.