When to unsubscribe a subscription

Question

I have a question regarding how to unsubscribe an observable. I have two codes and I'm not really sure about which one is better.

Example 1 -> Unsubscribe the subscriber once the stream has finished:

Subscriber<String> subscriber = new Subscriber<String>() {
        @Override
        public void onCompleted() {
            progressdialog.dissmiss();
            unsubscribe();
        }

        @Override
        public void onError(Throwable e) {
            progressdialog.dissmiss();
        }

        @Override
        public void onNext(String s) {
            // do something with data
        }
    }

Example 2 -> Unsubscribe the subscription once the activity is destroyed:

private void test(){
    Subscriber<String> subscriber = new Subscriber<String>() {
        @Override
        public void onCompleted() {
            progressdialog.dissmiss();
        }

        @Override
        public void onError(Throwable e) {
            progressdialog.dissmiss();
        }

        @Override
        public void onNext(String s) {
            // do something with data
        }
    };

    subscription = BackendRequest.login(loginRequest)
            .subscribeOn(Schedulers.newThread())
            .observeOn(AndroidSchedulers.mainThread())
            .subscribe(subscriber);

    compositeSubscription.add(subscription);
}

@Override
protected void onDestroy() {
    super.onDestroy();
    this.subscription.unsubscribe();
}

I have to mention that my observables only will emit once, the activity should not wait for more calls from the Observable.

Which one is better?

Thanks in advance

Answer 1

There is no need to unsubscribe in onCompleted. Take a look at The Observable Contract

When an Observable issues an OnError or OnComplete notification to its observers, this ends the subscription. Observers do not need to issue an Unsubscribe notification to end subscriptions that are ended by the Observable in this way.

On the other hand, you definitely should unsubscribe in onDestroy in order to prevent memory leaks.