Rxjs: cache(), share(), publish().refCount() and publishReplay().refCount() do not work as told

Created on 1 Mar 2016 · 5Comments · Source: ReactiveX/rxjs

Hi,
I'm fairly new to RxJS, so this could be a misunderstanding, but for the following situation:
I have a Service singleton that queries a REST API, like this:

export class Service
{
  public get RestStream() : Observable<RestModel> { 
    return this.getStuff().publishReplay().refCount(); 
  }
...
}

"this.getStuff()" queries the API and returns an Observable
In my understanding, every further transformation of the RestStream in other classes shouldnt requery the API, because I cached it (Say for example I want a part of the RestModel and add a function somewhere that returns service.RestStream.map(<something>)). So any subscribtion to the service or depenent services that further transform the Observable should not requery to API.
I guess this is wrong, because I get plenty of requests in chrome to an url that is only requested in that getStuff() method.
What is the correct way to implement the behavior that I want? (I already tried the operators in the heading)

Source

jvanbruegge

Most helpful comment

@SuperManitu I have to say that @tbugrara is right on.

Think of an Observable like a function. In this case, it's a function that starts a request the first time it's called (subscribed to) and shares that request (or it's result) with everyone else that calls it (subscribes to it).

@tbugrara's example is exactly right. Also in beta.2 you can replace .publishReplay().refCount() with .cache() as they are the same.

benlesh on 1 Mar 2016

👍6 😕1

All 5 comments

I'm still new to typescript, but I have a feeling that it's because every time you call the getter, it creates a new observable. Try something like this?

export class Service {
    private _restStream: Observable<RestModel>;

    public get RestStream(): Observable<RestModel> {
        return this._restStream;
    }

    constructor() {
        this._restStream = this.getStuff().publishReplay().refCount();
    }
}