CODEWITHSUNDEEP
javarx-java
Nitzan Tomer
Nitzan Tomer

Reputation: 164147

PublishSubject to fire onNext when subscribed

I'm trying to create a proxy to my models using RxJava, this proxy lets other subscribe for changes in the model.

Here's a simplified version of my proxy:

class MyModelProxy {
    private static MyModelProxy instance;

    private MyModel model;
    private PublishSubject<MyModel> subject;

    private MyModelProxy() {
        this.model = // load from cache
        this.subject = PublishSubject.create();
    }

    public static Observable<MyModel> observe() {
        if (instance == null) {
            instance = new MyModelProxy();
        }

        return instance.subject;
    }

    private void modelUpdated() {
        this.subject.onNext(this.model);
    }
}

There's only one instance of MyModel in the system, but it might change over time, and so I want to be able to register for these updates.
This code works well if I register on the Observable returned from the observe method before calling the onNext of the subject.

The behavior I want is that when the subscribe method is called on this observer then the current instance of MyModel will be sent to the subscriber that just subscribed.

I thought about extending the PublishSubject but it's final, so I thought about writing my own version of it (mostly by copying what's in PublishSubject and adding what I need) but then I found out that SubjectSubscriptionManager has package visibility so that's a dead end too.

Any ideas how I can add this needed functionality?
Thanks.

Upvotes: 0

Views: 416

Answers (1)

m.ostroverkhov
m.ostroverkhov

Reputation: 1960

There is also BehaviorSubject, which does exactly what you want: emits most recent and all future items to its subscribers

Upvotes: 1

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