Subject subscription not completing

Question

Here is my scenario. I have a class for mongodb access. On initialization the connection is made and saved in a ReplaySubject. Consumers get this subject, and use it to do the database reads and writes. At that level it all works as expected.

public getCollection(collectionname: string) {
    // console.log('getCollection mongodb', this.mongoclient$);
    return this.mongoclient$
        .map(db => db.collection(collectionname))       
}

The consumer gets the value, then does the reads and writes in an observable chain. The consumer may call this function before the connection is made.

But if I use concatMap in the chain, it works once. Same with other apis that act when the observable completes.

concatMap stops working because the Subject doesn't complete.

So how do I get the value from the Subject in a way that the observable chain completes?

Or maybe I'm doing it wrong. What would be a better way of doing initialization to get a value, an asynchronous process to get the value, where consumers could call for the value before it is acquired?

Derek Kite Derek Kite · Accepted Answer · 2018-01-25T06:20:52

.take(1) is the answer. This would work only in the case where you need to get one value and operate on it down the observable chain.

Thanks to Alex Rickabaugh on gitter.

Subject subscription not completing

1 Answers